Please Peter assist me

I lost my phone at the end on November 2021 my phone was insured and the day I signed phone insurance form sales personnel told me if I loose the box with IMEI number I will not claim the phone, from December 2021 and January till the end of February I was looking the box with IMEI number in my house I didn't find it. I went to the shop outlet to cancel the insurance they advised me to contact the insurance company for cancelation. The person handling my cancelation provide me with the IMEI number. I then continued to claim the phone from insurance company but the claim was rejected they said I claim after 30 days but I told them was not my fault the sales personnel gave me wrong information on how to claim when I lost my phone. Please help me Peter I'm still pay insurance for nothing.