Unfair treatment due to system changes at MTN

I have been a loyal client of MTN since 2007 and I have lost complete trust in them. I have paid via eft for the last few months as I have been struggling to change my debit order. As I do every month payment was made from my beneficiary list, same as always. However this time they claim to not have received my payment. I spoke to an agent who politely said sorry, the systems have changed this is why I am experiencing this problem. Now how, if the systems was changed does it become the clients problem because they cannot pick up a payment. I used the whatsapp number to send the proof of payment also to no avail. This is really unacceptable service, which in turn effects my credit ratings. I do believe that this is very unfair.