Cellular Update Failed

Hi Apple ,

 I have got an I phone 7 (model A1660) with the serial code F7****G6W that have recently updated but since the update was done my cellular antenna is completely disappearing! and due to that I can not make phone calls or text or anything :( could u please help me out here and tell me what to do to fix it ??? 

ps : since this problem was caused by the new update of Apple to my phone and I did not do any thing to it, is there any chance that i can change this phone with a new phone ? if yes ,is it for free or it will cost as much as a new phone ? or maybe I can bring this phone to repair it? if yes, I would like to know the repairing cost if possible.

I look forward to hearing from you soon.

Thank you

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