Upgrade Cancellation gone wrong.

My name us Tiny Suzan Khunou, a 57 year old mother and grandmother from Rustenburg. In May 2022 I ungraded my contract phone to a home wifi router but to my disappointment the internet connection was not picking up in my area which is Tlhabane which I was told it would but never did. I sent back the device within 10 days of leu and asked them to put me back to contract because I was only left with 2 months to end the contract and I was told that was done and all was well. A month later to my surprise, I don’t get credited with the airtime and data as usual and I get a statement that said I must pay R4004. I called them and I was sent from pillar to post until they agreed that the fault was on their side. Now this issue involves Mondo which I am not sure if it is a company which works with MTN or not but MTN said I should call them and they should give me credit for the cancellation of the upgrade and the cancellation of the entire contract as they did not follow my instructions which was to keep the contract for the remaining months. It has been 4 full months now with this issue and my account keeps going up. We are now at R4500 which is money I do not have. I need urgent help with this issue please.