Contract upgraded without my approval

MTN upgraded my contract from a fixed amount of R79.00 per month to R899.39 per month. When I asked for proof of upgrade MTN could not provide any evidence (I suspect some inside job). <br> <br> Anyway to make matters worse, I submitted all documentation MTN needed to investigate on 29 Oct 2015 and informed MTN in writing not to debit my account until the investigation is done. As expected MTN did not get back to me but come 26 November 2015, MTN went ahead a debited my account again. <br> <br> I was told my the MTN Customer Care consultant that I must follow-up with MTN store (talk about passing the buck). I told this MTN Customer Care consultant that I won't be abused and I refuse to do the follow-up with MTN store.<br> <br> I guess my only option is to contact the Regulator. I now understand why the Nigerian Regulator has imposed a R$5.2bn fine, MTN is a law unto itself.