Disappointed at MTN

On the 3rd of May I paid my bill account on an ATM in the embalenhle branch and accidentally punched in the the wrong reference number, when I tried to contact mtn regarding the matter one of their champions said I need to provide a proof of payment for them to allocate my payment to the relevant account which is mine, before going to the bank to request the proof of payment i paid another R500 towards my bill account on the 21st of May because my services were going to be stopped i then went to the bank to request proof of payment because that day 3rd of May the machine did not dispense a receipt for me I then sent it to mtn I've even lost count of how many times I've been sending it only to tell me today that it's not valid and I don't understand how it's not valid when it came straight from the bank I'm very dissatisfied and unhappy with their service because now I've paid for someone else's account and my services are going to be stopped because they are failing to do proper investigation on this matter. I've been calling every after two days for follow-up/feedback they are busy telling me that they are escalating the matter to the relevant department every single time and finally BOOM "please provide a valid proof of payment" because the one you sent is not valid I don't know which one I should send now . I used to speak highly of mtn but after this ai no shame you just don't care about your clients and the service you provide