no service

I loaded R30 prepaid airtime and made two calls to mtn numbers. Both calls together was 3minutes. I sent 1sms to an mtn number. When I checked my balance now it was only R9.00 left. I tried calling customer service, but the line just cut. This is not the first time and non services fom mtn. The website says 24/7 customer service. I've been a very long client of mtn and for them to rob my airtime like this and i cannot even query it. Your service has become horrific.