IPhone 4 won't connect to Wi-Fi after screen being fixed?

My iPhone 4 was working perfectly for ages, even when the screen was cracked. I took it to get the screen fixed because it looked bad, but now after it has been fixed I can't connect to my Wi-Fi properly.
At first, my phone couldn't connect to ANY Wi-Fi connections (there are usually connections from next door) but then eventually my Wi-Fi began working. I then went out of the house and when returning my Wi-Fi didn't come back on, and I couldn't connect to anything. Everyone else in my house has their iPhones connected and working fine.

Extra information: The front & back of the iPhone was cracked, so they were fixed as well as the home button which was broken.
When doing the fixing, the sim card was taken out (I'm not sure what the reason for this was) and then put back in afterwards.

Give it to repair back and say your problem may be he forgot to put antina in it