How hard can an account query be to resolve?

I made a payment on my account and used the incorrect reference number so the payment is not reflecting on my account (my mistake I am aware). I have been trying for more than a week to have this rectified and no one has been able to assist. I have called the stores they say they no longer have access to account services and that I am to call the MTN call centre which either never answers (hold on until the line drops) or you hold on for 20+ minutes every time. So quick to call 10 times a day to upgrade but cannot assist with a simple account query?? MTN is truly ****ing me off!!!