Airtime and data depleted before I even used them.

I am getting very frustrated with MTN and honestly have lost my patience with this network.<br> Lately my airtime and data just disappear with no explanation. For example yesterday on the 14 July 2015<br> I received my monthly top up of R100.00 of airtime and 100 MB of data and this morning it was depleted with no explanation.<br> I have called several times to try to cancel my contract with MTN but the call centre is useless it's either there's no one to answer,<br> or they finally answer after hours and tell me that the retentions department will call me back because an email has been sent to them re my cancellation,<br> This has happened 4 times in one month I'm still waiting for retentions to help me get out of this contract, because I don't know what I'm paying for. I have no choice but to stop the debit order<br> to MTN because I no longer want to deal with them, so maybe if I stop paying they will call me back.<br>