I got a call from the telemarketers, they advertised a contract sim with 20GB of anytime data, 5 GB of YouTube, 2GB of night surfer

I got a call from the telemarketers, they advertised a contract sim with 20GB of anytime data, 5 GB of YouTube, 2GB of night surfer.after a day of receiving the sim card, it turns out that it was actually 20GB if YouTube, 5GB of night surfer and 2GB of anytime data. I logged a return, i was not assisted for 2 years. Requested call records, then the sim card contract was terminated,. A year later i then received a letter of demand from MTN stating that i owe them