over charged

I bought a couch at home choice in April, I ordered it online and it was R3999.00 instalment was R398 pm. Later in the month i got a call from their sales agent confirming my order, she told me that the 2 seater couch is out of stock but there is a 3 seater couch which is bigger and better for only R498pm, i told her i am not interested in that 3 seater i want what i ordered if it not there they should just cancel, she insisted and i still refused, later on that day she phone again saying they found the 2 seater couch and they will deliver we greed on the term and condition and that I was going to pay R398 pm.The couch was delivered and i was happy until i received and sms reminding me of the payment i need to make for R518.00 i phoned Home Choice regarding that and they said that is my instalment I then requested for them to send me a telephone recording of me agreeing to pay the R518.00 and i was kept on hold for 10Min, i later spoke to Angela who gave me a reference number (***) and said she will excalate the quiry. its been 10days now no call from them except the rude collection agents telling me I made a short payment because i paid R400.00. I need the recording please!