Overbilling & no feedback

My contract migrated from Nashua Mobile Dec 2014 from when i also changed my contract.Over the next 3 months i was in on-going dispute with the Branch (Cresta) on overbilled charges.This was eventually resolved for future debits but i was still getting no resolution to the refund due for previous months. I eventually went to MTN 14th Avenue first week in March where i was attended to by Ronzley du Plessis.He noticed that the credit of R129 was reflected but not matched against my account.He assured me that this would be off-set against my end March deduction. This did not happen and he refuses to respond to any of my emails even when i threaten escalation.This 'no feedback' is typical of many issues i have had with MTN over the past 4 months - in fact your Customer Services division is absolutely hopeless.Other than the auto-response to emails, they refuse to acknowledge any queries or complaints.