Home router

I took a home router contract with them in April and it was never working when it got delivered then I called them and told them the problem and I was told by the consultant that I should take it to my nearest mtn store they will help me and that’s what I did. It never worked after that I called again and told them it’s not working then they told me to move it around the house it will eventually work 2 weeks later still not working then I decided to go back to the store to cancel it then I was given a cancellation code a week later After receiving the code I sent them an email on cancellation then they acknowledge it then they sent me an email saying my contact was cancelled in June but now my problem starts when now I’m getting a statement from Mtn that I’m owing them R6200 for a router I cancelled within 2 months and the initial debit order deduction was R300 so I just want to know from @Mtn how did it get to R6200 with only 2 months of no help from them and cancellation cause now I’m escalating this matter to the ombudsman!!