Billing me for an account that isn't even open

I am tired of dealing with this useless company and this is exactly why I left as soon as I could after being forced to go back to Autopage when Nashua Mobile sold off their subscriber base. My contract finished in December 2014, I was still billed in January to which I told Autopage I will not pay the invoice due to my contract finishing in December and the fact that I had requested the contract does not continue. My number was ported to Telkom in January already and I have continuously received messages to pay the outstanding balance. Today I finally receive a message stating that my request for credit of R648.79 has been sent through, only to receive another message stating that I now owe R1266.81. I have since received an sms stating that the credit for R648.79 was successfully credited to my account but it shows an outstanding balance of R618.02. How is it even possible for you to have another invoice for me when my number was ported to Telkom in January. You don't even own the number and are still sending me an invoice for it? Sort this and rectify all faults at the credit bureau immediately or I will disclose how you blatantly try and cheat people out of money.