Dispute of claim outcome MTN Insurance

Am disappointed with @MTNsouthafrica insurance I have a contract with MTN took a insurance on my phone . I Submitted my claim three weeks ago with no phone . Today I was told the claim was rejected due to my sim not being in use when the phone got lost which is not true. I have never removed my sim card on my phone since I bought the phone never . I will like MTN to explain to me how it came to that conclusion .