Billing for a closed accont

Hi Telkom, <br> I closed my account and paid final amount, and received confirmation that my account is fully settled on the 25th of May 2015. For the account closed on the 15th of May. Today I went to my old address and yet to receive a bill for R 853.10! Now this is affecting my credit record, because you continue to bill account that has been closed. I don't have a Telkom landline to call for free, and certainly not going to spend another rand to get this sorted. This is not acceptable. Please resolve this issue asap!