"Note that any purchased Rebtel credit will expire after twelve (12) months of inactivity."
I'm one of their customers. My credit is gone without any reminders or notification. I have been left in dark until I tried to use the service yesterday and found out that my credit is gone. The credit is literally my money.
Comparing to what Skype does (https://support.skype.com/en/faq/FA10378/how-do-i-reactivate...), this is totally irresponsible and unacceptable to me. They provide no way of "reactivate" the credit.
So guys, be aware of such irresponsible service providers and check your provider's terms.