Not able to make phone call after purchased one month unlimited plan

I am really disappointed with fring! This is not the first time, I paid for one month unlimited plan, even I received the receipt confirmed that I have already paid for the service, but I just cant call! Every time, fring keep giving me message saying that I dont have enough credit! Last time, it happened the same until 10 days later, fring finally showed my purchased! But I already lost 10 days! This is absolutely not a fair business! Fring customer service is horrible, you can never get answer from them!

dayuku about fring, v7.0.0.6