MTN wanting to charge me for a router that has never worked while I still fully paid for it each month

Had a home router contract with MTN! The rougher has never worked no matter how much we tried. There was even a time where I called MTN regarding the issue. Umpon expiration of the contract I then took the rougher back as I was told I need to take it back! Now I get a message that the router has failed assessment as non functional! This router has never worked ever since I took the contract! As evidence them MTN must check the usage and see if this rougher was used to its full capacity! I cannot ba taken for a ride where I paid the duration of the contract for something that never served my needs, now I’m being told it’s non functional! That means it was non functional when it was given to me! MTN you can’t be ****** like that! Check the usage history of that thing and see for yourselves