Horrible Service from mtn

I took a contract for an iPhone, they did a Debi check of more than R3 000 though my monthly contribution is only R1 050, from day one the SIM card was never wording and month end R800 was debited and today I got sms’s saying I’m owing R1 224,74, I was helped by Sipho from Southgate MTN who is always ignoring my emails and take days to reply, I’m still using my old SIM card