National Insurance Company — Phone insurance claim declined

I bought oneassist protection plan last year in september for my smartphone, at that time i was under 18 and there was nothing mentioning that you have to be above 18 at the time of buying the plan if you want to claim it in future. And now when i need it they are declining my request by saying that you are an underage customer even though now and even on the time of accident i was 18 plus. So it was basically useless for me to buy it in first place. I want you to accept my claim so that i can get my smartphone fixed.
Invoice Number # EAAAAX[protected]