I use nonoh.net. It has very good sound quality and

never broken, Only problem is that it some times not set your CID correctly, but it will set your CID at the first time when you start to use it. Nonoh provide 4 months free time for every time you paid and charge later months. It equals to 0.7 C/M, that is 1000/$7. this is a good deal.

The voipdiscount.com is in the same group of Nonoh.net, which I think may has the same quality, but I never tried.