Inaction and Despicable Customer Service from MTN

My MTN account is paid regularly as a scheduled event before due date yet, on two occasions, MTN have allocated my payment two weeks after i have paid the account - this had now had an impact on my credit score. Despite submitting proof of payment to them on six occasions, sending emails to eleven different people in either their customer service or legal department, their response is to ask for the information to be re-sent, or not to respond at all. This has been going on sine December 2023 and the late allocation of my December 2023 payment was probably due to someone being on leave. To indicate just how poor they are at customer service, i have emailed numerous other people in their company without anything being actioned.