I use Voipstunt over 9 months. Always feel good for its service.
One issue makeing me not happy is it changed country list of free call without email the notice to user.
Ok. I check the call history. Phone calls to China are charged 0.7 cent per minute. USA is still free.
I may change to other service provider, when both USA and China are not free.
So, it is time to do some research to find a second choice for backup.
Currently, Voipstunt has an un-expired credit plan.
Keep calling every day untill all free calls are not available.