Ethics and service at question

Pre 2020 I had good service for close to 12 years with my cellphone contract.I had some online banking ***** happening to my banking account and it caused a few issues to my debits.It affected my MTN contract and I resolved matter with bank and payed in to square cellphone account,then I had to continually pay in but I had a debit facility setup.Due to Covid there was limited service by the wall in branch where I regularly update my contract,etc.also Covid made it difficult to get to their payment structure and my line was disconnected.Hiw they want me to contact them after that was very odd until they requested I make payments for outstanding amounts but the duration has lapsed in this time.Now they want me to pay and I'm owed data,airtime and services they didn't uphold in the duration of the 24 month contract.Also there is no statement seems I have to rely on what they say I owe.Currently I'm still paying there was a time I was told I have to pay an amount to be payed up.Done that but still in the same boat.I have since switch to prepaid as my contract number was useless.I was very dissatisfied with this service as I have been with MTN for 14 years.