MTN Insurance unreliable

I took a signed a contract and insurance for my Iphone8 two years ago in 2018. Last year December 2019 unfortunately my phone screen cracked and MTN took it in for repairs then after months my phone required to be on the charger permanently. How am i going to be mobile with a phone that has to always be on a charger? So i took out my sim out got a got another phone as an interim so i can be mobile meanwhile getting hold of MTN. Now i am responded by a company named Guard Risk saying that they are my cellphone insurer, like what on earth is happening when did this happen without my knowledge. Guard Risk is refusing to fix my phone because i took out my MTN sim, how can i use the phone if it cannot be mobile. Can MTN fix my phone like how you deduct money from my account without any hassles.