FRUSTRATED!

Since my JET Account has been handed to these people I have been struggling tremendously to have my payments I make to these people reflecting on my account. I sent my proof of payment through to them every month, but still it is such a huge struggle to have my payments reflecting on my account. They bombard me phone calls and the more I tell them I did make payments the more phone calls I get. I use the correct reference number provided by them, I make my payments timeously. Please tell me what I should do further? I am tired of struggling like this every month, sending emails after emails and only receiving replies after 2-3 weeks apologizing that the payment did not reflect.