False advertising leads to big frustration

It all started in middle March when a HP 15 laptop was advertised in the Telkom booklet. I app**** for the laptop and waited to be approved. After being approved I went to fetch the laptop, but I received the wrong laptop. I went back to the shop and took everything back and was informed that they will order the correct laptop. After a few days I received a phone call informing me that it was mistake made in their booklet. I subsequently went to cancel the contract and was informed that there will be no charges as I cancelled the contract before the cooling off period. At the end of March I received an invoice from Telkom stating that I owe them the monthly fee for the contract which I cancelled. I went into the shop again and needed to fill in a cancellation form again. At the end of April a debit order went off my bank for the amount on the invoice. I phoned into the call centre demanding my money back. After my money was refunded, I received a written promise that they will not take money from my account again. But at the end of May they took money from my account again. The matter is still not resolved and they are charging me a R5000 cancel fee, for a thing that's their fault