SIP Provider Comparison

pbx phone systems for business
Aimee profile image

Our site is reader-supported – by clicking our links, we can match you with a potential supplier, and we may earn a small commission for this referral.

Make calls to the PSTN network from your VoIP system with the help of these SIP trunk providers

If you’re searching for SIP trunk providers, you’re either investing in a brand new VoIP phone system or looking to scale up an existing one. Thankfully SIP trunk lines are easy to install, add, and even take away.Even better, because SIP trunks are virtual telephone lines, they can carry internet data, video, and voice data on one line. This makes virtual phone lines far more cost-effective than traditional phone lines.If you’re looking to invest in a brand new VoIP phone system, most providers will include SIP trunking in a hosting package. Businesses that self-host or are looking to self-host a VoIP phone system have a huge variety of SIP trunking providers to choose from.

Here at Expert Market, we’ve conducted research into SIP trunk providers. We’ve detailed the best of the bunch in the section below. But if you would like to learn more about what SIP trunking is,skip ahead to our FAQ section where we’ve answered some common questions.

The Best SIP Trunk Providers

Our research revealed that the best SIP trunk providers are:

  1. Verizon
  2. Vonage
  3. Digium
  4. UniTel
  5. Mitel
SIP Trunk ProviderBest For
VerizonBest for contract-free services
VonageBest for medium to large businesses
DigiumBest for small businesses
UniTelBest for cheap SIP trunks
MitelBest for SIP trunk/VoIP package

1. Verizon

Best for contract-free services

Verizon is one of the biggest telephony names in America, so it makes sense that it’s paid special attention to its SIP trunk service. Its SIP trunking is designed to work with any IP PBX (internet enabled private branch exchange) that supports SIP-based Trunking, and it promises better cost control, and a fast and highly reliable network – great news for growing businesses. Best of all, it delivers all of this completely contract-free!


  • Uses a standards-based quality of service scheme
  • Government standard technology
  • Very reliable network


  • Customer service can be hit and miss
  • Pricing isn’t transparent

2. Vonage

Best for medium to large businesses

Vonage is best known for its full scale VoIP solutions, but it also provides SIP trunking too. Its SIP trunks are completely compatible with your legacy system, and you can customize the system to include as many lines as you wish. With the SIP trunks connecting to Vonage’s reliable Cloud system, your business’ communication system should never go down.


  • Industry-specific solutions
  • US-based customer support
  • Very competitive rates


  • App not as featureful as others
  • Previously had a few issues with billing

3. Digium

Best for small businesses

Digium offers three SIP trunking Plans, two of which are contracted – however choosing a contract does mean small businesses have complete control over call costs. This is because you know exactly how much your business is going to pay each month. And if you happen to make more calls than usual, you don’t need to fret about a ballooning bill. The contracts include unlimited inbound and outbound calls, free setup, and you can easily add or remove lines as and when you need.


  • No setup fee
  • Transparent pricing
  • Lots of SIP trunking features


  • Cheapest contract lasts three years
  • Not suitable for larger businesses

4. UniTel

Best for cheap SIP trunk provider

Digium offers three SIP trunking Plans, two of which are contracted – however choosing a contract does mean small businesses have complete control over call costs. This is because you know exactly how much your business is going to pay each month. And if you happen to make more calls than usual, you don’t need to fret about a ballooning bill. The contracts include unlimited inbound and outbound calls, free setup, and you can easily add or remove lines as and when you need.


  • Cheap rates
  • US-based customer support
  • Strong network reliability


  • No free trial
  • Only suitable for small businesses

5. Mitel

Best SIP trunk/VoIP package

Not every VoIP provider offers its own SIP trunking service. Often, they’ll use a third party provider, which means you may not be benefiting from the cheapest rate. Mitel uses its own SIP trunks when installing a VoIP system which means you’ll only ever deal with one provider. With a huge range of industry-specific VoIP solutions available, Mitel is a great option for anyone looking to invest in or upgrade a VoIP phone system.


  • Industry-specific packages
  • Huge range of VoIP products on offer
  • Supplies scalable VoIP systems


  • Not the cheapest option
  • Pricing not particularly transparent

Expert Verdict

SIP trunks enable you to make the most out of your VoIP phone system for a much more reasonable cost. In fact, some providers say you can save up to 40% by switching from traditional phone lines to virtual SIP trunk lines.

SIP trunks all do the same thing, no matter which provider you choose. So when it comes to choosing the best SIP trunk provider for your business, you need to consider other factors. This could come down to whether they cater for large businesses, customer service, or even whether they can provide you with a satisfactory quote.

Make sure you compare quotes before you commit to a SIP trunk provider. That way, you know you’re getting the best price for your business. Expert Market’s price comparison service provides you with a quick and easy way of doing that.

All you need to do is fill in our form with a few details about your business and the best SIP trunk providers for you will be in touch.


1. How Much Does SIP trunking Cost?

SIP trunk pricing can be calculated on a pay as you go or contract basis. Pay as you go rates can differ between $0.0070 and $0.0098 for the termination of inbound calls, $0.0045 to $0.012 for outbound calls, and around $0.018 to $0.019 for toll-free inbound calls.Alternatively, contracts can start from as little as $19/month (the cheaper the price, the longer the contract), to usually around $25/month. These prices are for calls only, and don’t include additional feature packages.

Many companies see SIP trunking cost savings of as much as 30-40% when they switch from traditional phone lines. This is largely down to the fact that SIP trunking is available on a line by line basis, and minimal hardware installation is required.

2. What is SIP trunking?

SIP trunks are virtual telephone lines that act as a bridge between your VoIP system and the PSTN (traditional telephone network). Voice, video and digital fax data travels from your VoIP handset via a SIP trunk to a hosted or self-hosted private branch exchange (PBX), before being released to the external telephone system network.

This ability to carry voice, video, and fax data on one line enables your business to make the most out of your VoIP system, without paying over the odds for seperate lines to carry each data type. This means SIP trunking is ideal for businesses looking to cut down on outgoing costs.

Your phone system will be able to decipher whether the receiving system is traditional or VoIP. If the receiving system is VoIP, digital call data travels from your SIP trunk to a data center, before continuing as digital data to the receiving SIP trunk.

If the receiving system is a traditional phone system, your digital call data is repackaged into analogue call data by an FXO switch. The call then continues its journey from the switch to a PBX, before entering the traditional telephone network, where it is rerouted via the local telephone exchange.

3. What’s the difference between SIP trunk Lines and traditional phone lines?

This table provides a breakdown of the differences between SIP trunk lines and traditional phone lines.

Physical lineVoice dataVideo dataSusceptible to damagePurchase one line at a time
SIP trunk
Traditional phone line

SIP trunks are virtual lines, which means they allow the transfer of voice, video, and internet data. Traditional phone lines are physical, and are only compatible with voice data. This is very limiting in an age where video calls and call data collection are integral to the growth of businesses.

Traditional phone lines are also susceptible to damage in the event of bad weather or a natural disaster. Because SIP trunk lines are virtual, all it takes is a little rerouting to an unaffected data center, and your phone system is back up and running.

As well as all this, traditional phone lines require businesses to purchase up to 24 channels at a time (even if they only needs one more channel), whereas you can purchase SIP trunk lines one at a time. This also means you can take away lines if they’re not required, so you’re never paying for lines that you don’t need.

Plus, because traditional phone lines are physical, they’re more expensive to install. SIP trunks are virtual, meaning they don’t require any installation. This factor means the cost of your phone system is immediately reduced.

Written by:
Aimee profile image
Aimee Bradshaw Writer and researcher

Aimee is Expert Market’s resident telephone systems and point of sale go-to. If she’s not writing about business products, you’ll find her daydreaming about dog walking on Dorset beaches.

Reviewed by:
James Macey Senior Business Software Researcher

James thinks all businesses can improve if they use the right technology. At Expert Market, he utilises his 4+ years experience as a researcher to offer specialised advice on a wide range of categories from CRM to Fleet Management.