Well I don’t have a Voip service, but I use T-Mobile’s UMA feature, which allows me to make calls over any Wi-Fi connection. The min I use over it come out of my monthly allotment, but if I paid 9.99, I could get unlimited min over Wi-Fi. I know this isn’t probably what you’re looking for, but if you’re already with T-Mobile, it’s an awesome choice. It saves a lot of money. Call quality is also great as well, and you won’t have to worry about “reception” like you would with a regular phone.