IPhone randomly saying invalid sim?

So I bought an iPhone 7 from someone I knew that was stolen. I paid 25 for it then spent 80 for a guy to jailbreak and remove the iCloud. He put something on the SIM card and told me not to take it out. The phone works perfectly but maybe after 2 hours it'll say invalid sim then I have to restart and it'll be back to normal. What should I do and I don't really have the money to get it checked out again.

Generally that's what you get when you do a hack. You need to ask the guy you paid for the sim if the situation can be improved, but I'm sure it's something the cell phone company is doing because the phone is black listed. You should have just paid $100 for a clean iPhone 6S on eBay, it's basically the same thing as an iPhone 7.

Take the phone to the Police and tell them who you bought it from.

Hopefully you will not be prosecuted for handling stolen property… Then consider the waste of money as a learning experience.

The phone has almost certainly not been unliked from icloud, the connection attempts are just being blocked. If it ever updates are reconnects, it's location will be registered together with fact it is stolen - they you can expect a visit…

1 don't buy a stolen phone and 2 don't buy a iphone!