Pathetic support from accounts department

I have never in my life received such pathetic service from an accounts department. I made an online payment on 31 October which has still not been allocated to my account. I have since send 25 e-mails, phoned 15 times, spoke to supervisors, have reference numbers AND STILL no allocation of my payment has been made. I have now received endless calls, SMS's and emails stating that I am in arrears and even threatening that I am now placed on ITC!!!!! FOR YOUR MISTAKE!!!. Everytime I start the whole process from beginning and still no-one from the accounts department is able to help me. This is absolutely unacceptable! My issue is still not being handled even though I was promised that the allocation will be made within 10 working days, which is now 20!!!