Paying customers account terminated and handed over

I have been having an MTN account for about 3 years now, it was always on debit order, last year the debit just stop I didn't notice until they suspended the accounts I then tried to pay extra fell behind due to personal reasons in beginning of the year ever since then I have been paying a lot extra to get the account up to date as much as I can. Monthly installments were R3400s I have been paying R5000 to R9000 per month to clearly get the account up to date. Just before the account is up to date with less than a month's amount outstanding something in R1000s MTN cancelled my contract and request I pay the full outstanding for the account which is just over 2 years pre term. I have come in contact with the company they've handed me over to and after requesting my statements they've said that they don't understand why MTN has handed me over now instead of when the account was actually behind and the account is basically almost up to date now they've said to sort it out with MTN I have gone in store the agent has showed me that the account was barely outstanding with about R1k only and he can see the constant large payments I have made and he too doesn't understand why the contract was terminated since they cannot do that to a paying customer and it showed its only on a pre hand over he has put in a dispute but 3 weeks later he said it remains unchanged. Today I have spoken to MTN they said I must contact the company the have handed it over to which is SSDA but SSDA says they cannot help me their job is only to request the full outstanding amount of the full contract amount that remained. No one can help me and I refuse to accept the termination of a paying customers account.