Stuck in restore mode

I got my iphone on Christmas of 2021 and it was running well until I needed to update it, the phone would act like it's about to update until it got to the end of the update. But right before it finished it would say "not connected to network", and I tried it again, and again, and again and it said the same thing every time. Then I tried to update it using itunes, and it kept saying the same thing. So I just decided to restore (reset) my iphone and it's been stuck in restore mode ever since. So then I took it to best buy and they did the same thing I did and it didn't work and they said "you might just have to buy a new phone" and I feel like they probably know how to fix it but just want me to buy another phone and I know there's probably a way to fix it.