********** Upgrade on my Expiring Contract

Recently got a nice little gift from MTN telling me that instead of paying off my last R119 on a 24 Month contract which I was finishing of this month( February 2018) to close off a 24 month contract, I will be paying R799 for an upgrade that I did not do. And what annoys me the most is that, the contract was upgrade in KZN in December while I was in Gauteng, as I was working through December. But what annoys me the most is the bad service and the lack of assistance, and being given numbers that don't work in order to get assistance. I have lodged a ***** complaint with MTN, but now my biggest concern is what happens now as one of your agents says that the investigations can take months, I do not want to be in a situation where my credit record is now being tarnished due to this. I am also trying to update you with my contact number so you can contact me through this process, but it doesn't look like I can do that, I have tried contact, ********** , 083 173, ********** 867, ********** 831, those are numbers I received from your agents and they all don't work. Will I be billed for this contract while this is being investigate... I am willing to only pay for the last R119 installment