Payment not allocated to account

I have always made payment using my card number as reference. However, for the past 2 payments, the accounts department is not allocating my payment. I have sent through the proof of payment 3 times to [Email Removed] but I still get SMSes and calls saying that my account is overdue.<br> <br> now they are saying in the proof of payment email, I must use my account number as reference and not my card number as the subject of the email. But when I send through the email with proof payment, I receive back an confirmation email with \useful tips"that says the subject line of the email I can use my card number. I have now sent through proof of payment using my card number and my account number but still no feedback except to say that they are handing me over to TCI. This is my last resort as they are not getting this - what do the people in the billing department do there?! Because when I called them this morning to resolve this"