MTN insurance claims

I took a cellphone contract which is coming to an end this month. They sent me emails and called for upgrade of which I upgraded to IPhone 16 and insured the device. The device was ****** I sent a claim but they declined my claim because of I was not using the mtn simacrd in the lost device.I did explain to them I was not using the mtn simcard the the phone because I do not have access to full benefits due the the mtn MoMo app registered under someone's details. I did call them and enquire they said there is nothing they can do to change the momo app registration. How fair is it to to use a simcard that I do not have full access for???