After updating software, phone shows mobile network not available

I have searched everywhere tried everything, from network resets to factory data resets, to clearing all ca he in the android boot screen. I've tried the mobile network settings, and putting a different Sim card into the phone. I even sent it in to samsung because I thought it was still under manufacturer 1 year warranty and hey refused to fix it due to the power button cap being missing (power button still work but the silver cap is missing) this happened when I took it out of the phone case it was in... and this apparently qualifies as "physical damage to the product" which voids the warranty. I have tried to get them to explain how the missing cap causes this issue and they just say " were sorry but this is our warranty policy"...

PLEASE HELP

I have a picture if it helps but it's just a screenshot of he box saying "mobile network not available"

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