Declined my claim and poor service

I have been your client for over a year, I have covered my cellphone with you. Last week, I put in a claim, and now they're saying it's rejected since my cellphone number doesn't match the number I was using. I called to change my cellphone number at first, but they did not explain anything to me, and I sent an email to change my cellphone number again in July. My phone number was changed, but now they say that it was only my contact number that was changed, not my cellphone, which was covered by your company. Why didn't they ask me? How is that my fault? How can I change my contact details without changing my phone number? when the cover is for a cellphone. Your service is very disappointing to me.