No Service and Searching. IPhone 3GS

Yesterday my phone would not get any service even if I was in a serviced area. The morning I had it, it was working fine. I gave my phone to a friend so he could replace my battery. I got it back and he said he couldn't replace it. When i got it back i could not get any service. I checked to make sure what he did and all he did was unscrew the screws and put them back. I've tried putting it on airplane mode and resetting the networks and checked if I needed to update but nothing works. I put it on 3G mode and it only went to one bar, sometimes 2, and once 3, but now it has no service at all. I really want to fix it because my iPhone is broken enough lol. Any suggestions?

Added (1). yesterday morning*

Can't activate Iphone 4

So today i bought a pre-owned iphone 4 at game stop. I get home and the phone works fine

i decided to restore the device's software to its original manufacturer settings.

the phone rebooted normally and i connected it to iTunes.

Itunes sends me a message saying - "( We're sorry, we're unable to continue with your activation at this time.) (Please try again later, or contact customer care.)

i'm not sure what the problem is? Why won't the phone activate? Aditional information i don't have a sim card for it yet.

any and all help is welcome thank you in advance.

Update 1: i also tried putting the phone in dfu mode and restart the whole process thinking it might help but no luck

I can't restore my iphone?

I changed my iPhone's pass code and forgot about it the next day. So I tried to restore it but my Mac says I can't restore it because find my iPhone is turned on, but I can't turn it off because it's locked.

Do they make clear and good quality rubber iPhone cases?

Where can I get one?

My phone has a thin case on it with my favourite band on the case. It's very thin and breakable. I want to protect both my phone and the case.

Where can I get something like that?

Price isn't an issue, as long as it is protective.