Mint (T-Mobile MVNO) has been great for me, $20/month/line and my one experience with international travel was good ($20 for 10 days). I used to be on Verizon and the quality of service doesn’t seem any worse while the price is dramatically lower.

Mint works well until it doesn't. I travel a lot and use voice over ip(VoIP). One day I called and got an automated message that my account needed funds. It didn't, my annual payment was months away.

My call to tech support was the generic worst. He insisted there was trouble with my current cell tower and I should reboot my phone. (ignoring the fact that I was able to get automated message). I explained I was using voice over ip, but the tech support didn't seem to understand that technology. Perhaps it wasn't in the script. I was on the call for about 30 minutes and eventually gave up. Phone started working about eight hours later.

Previous issue was with their roaming in foreign countries, however with VoIP that hasn't been an issue for years. So, a couple problems in about eight years. I rank them as one of the best among the terrible options.