"Sim Not Valid" on activation, faulty sim reader?

I am aware the obvious answer is "are you stupid, that means you're trying to insert a sim that the phone doesn't support because it's locked" however let me explain myself. i purchased this iPhone from a friend who has been using it on EE, when i got it, i accidentally ripped the battery connector off the motherboard so had to send it off to be re-soldered. I got it back, and it was on the activation screen where it says "hello" in all the language. After inserting about 5 different SIM cards all on different networks, it still says "sim not valid", even though i used the sim from my phone which i know works. It also says "no service" at the top so i am dreading that the sim reader may be faulty? Any suggestions would be appriciated!

Jacob