Poor service from Mtn online purchases

I app**** online for uncapped wifi bundel that was on premotion. When I recieved the router and sim card, I could not get the system to work. I was sent from one to the other Mtn service centre. I wanted to send everything back to Mtn but I got no assistance. Mow Mtn tells me that I am responsible for the service and it reflects badly on my credit report. Please assist me