Incorrect Device Sold, Cancellation not processed AFTER 3 MONTHS

Terrible Experience. Sold an incorrect product over the phone, a home router instead of a mobile router. Decided to go myself to MTN to return the product, By the way Mondo had sent me 2 of the same devices as a mistake, so I now had 2 devices. Anyway I returned both to MTN within 2 days of receiving them. Ref numbers RCO232593 and RCO232598. *********** people did not process cancellation even though I have ref numbers. Come end of July, I now get billed R1 300 for both. After phoning multiples times and going back to MTN main branch, cancellation only goes for processing on 10 Aug, Note I had returned devices on 30 May, almost 2.5 months prior and nothing was done. I am now getting billed again end Aug and both MTN and Mondo keep passing the buck to each other whilst I am caught in between waiting for my credit to be passed. Here's the kicker I am going to get billed this month an additional R1k, both of them know that my credit was not passed yet and yet both of them cannot stop it. THEFT !!! People at their worst customer service. Multiple phone calls to their customer service and everytime I get a different story. DONT EVER BUY ANYTHING THROUGH MONDO