Cheating so as not to pay out

I wrote last year in October to request changing my cell phone from a Samsung S6 to a Samsung S8. I sent all the details for the addition to Discovery, together with details for a laptop and camera. They added the laptop and the camera but not the Samsung S8. Now my Samsung S8 phone has been ****** and they are refusing to insure it because they failed to update the information according to my email. They are blaming ME saying that I have to phone Discovery to make any amendments to my policy, which is ridiculous because they added the other items but not the phone. I insist on a payout for this claim, or I will be taking all my insurance policies to another provider with a better reputation.