Bad service

I took out a phone contract with MTN in 2021 (Zevenwacht mall- Consultant Was Ncumisa)and took out insurance as well. My screen needs to be repaired (Dec 2023) however when I submitted the claim to mtn insurance (Admyntec) they advised that MTN submitted the incorrect device details and the device I have is not insured. So although this error was made on MTN side by Ncumisa, I am liable to paying the back bill of R800 in order for my phone to be repaired. This wasn’t my fault as all the documents I have, clearly has the correct information. I honestly do not understand why I am being charged for an error made by MTN.