Billing after account cancelled

I am a single mom of 2 and I was evicted from my rented property in August 2014. With a months notice, I went into my local branch (in a state of despair) and informed them of the situation early September. They explained that I would still be billed for September, which I understood and made a payment towards my arrears. I went in later that month and made another payment, where I was told that I was up to date on their systems. In my state of mind, I cant remember if I had asked for a receipt and I was living with my girls, literally out of our car! I have since been harassed by a debt collector who has just sent me the bills showing I was billed for October and November?? I dont understand and I honestly dont have the money or energy right now for this! I dont feel that it is fair that I did the right thing and made payments and somehow I was still billed for the months I shouldnt have been. I have discussed with friends and seems they have had similar experiences with Telkom, payments not being registered, being billed after closing their accounts... Please can someone assist with sorting this out, instead of threatening legal action...