Mtn - Bad service

I have changed my banking details almost 3 months ago but somehow mtn still debits from my old banking account even though the system shows that it has been changed. I am so fed up with this that i can assure you I will be cancelling all my contracts as soon as possible. I have been with mtn since 2012/2013 and there is no way i can do business with a provider that cannot even debit the correct account