Finding a reliable VoIP provider can be quite a task. This is due to the lack of standardization in the VoIP industry. So when you compare service providers all you have to go off are reviews from previous or current customers. What you need to know to ensure that you are doing business with a reliable service provider is to know what the VoIP provider is not.
1. Telephone Number Portability many people start using VoIP with a regular phone system. So you will already have a number which you own. So even if you switch your telephone provider you can still keep your number, thus you won't disrupt your services and lose any clients. However with VoIP if you want to change your services you will need to also change your number. Though this doesn't look promising you can work around it. The service provider for the VoIP service cant use your PSTN number so what they do is sell them and then lease them to you, this is why they don't allow you to take your number with you. You can easily transfer your PTSN number to your VoIP service for a small fee. If the provider tells you about this in advance then you can relax as this a good sign.
2. Partial VoIP and Complete VoIP there are some providers who use VoIP partially so they require you to make a call with your PTSN number to their service centers. This will then connect you to the place you want to call over VoIP. This requires you to keep your regular line as well as use the VoIP service. If a company offers this you should decline their services as it is not cost effective.
Keep these things in mind when you are seeking a service provider. There are indeed other things that can tell you if a service provider is reliable or not. Do your research so that you get the best service for the best price that meets all your business needs.