claiming to give you extra but taking from you

I am tired of MTN, every time I buy airtime I don't use it, they take it. I tried to call them, you hold when you about to reach the consultant they drop the phone.<br> <br> on Saturday I recharged airtime of 30 rand, I made a call of 2 minutes, later on when I wanted to make a call, MTN said I have reached my airtime that I did not even use.<br> <br> I am sick of this, I have lost so much money by using MTN, I am tired and porting my number to other networks.