Telkom does not acknowledge receiving payment

I was owing Telkom because I lost my job. In Dec 2014 I settled my account, using the reference number given to me in my account statements and took the proof of payment to Telkom store in South gate mall to be scanned and emailed to their accounts dept. A few days later i returned to check if my account was updated and it was confirmed that it was. I began receiving my invoices/account statements showing that my account was paid up and was no longer in arrears. I bought a prepaid simcard and loaded it with R1000 airtime to use for Internet and on 28 Jun 2015 I lost my Internet modem. I called Telkom to do a Sim swap and I was told that my my PREPAID simcard had been blocked because i owed Telkom from a previous cellphone contract I had with them. I asked them to check for my proof of payment as i had paid over 6 months ago and i no longer had the original proof of payment but they couldn't find the record of my payment even with the reference number i gave them. I still receive my proper statements showing that my account was up to date but i am told i never paid my account. I am not sure what is going on in their accounts dept but can someone please resolve this matter quick?