cellular update failed iphone 11 pro max 64 gb

[lider75]

Hello everybody.
i bought an iphone 11 pro max 64 gb in Doha airport on october 1st 2019.I was using the phone untill it tried to automatically update itself to ios 13.5.1.

[lider75]

Phone turned off and on and afterwards there was a warning sign on the screen as"cellular update failed".Because i bought the phone in a duty free shop i never had an invoice but a receipt from cashier machine and i fortunately it faded away by time so i dont have a proof of purchase and Apple turkey refuses to fix even i accept to pay for the repair.

[lider75]

can you help me about what to do please

[lider75]

is there a way to fix it by using 3utools?