No service or very low signal

[8Mislav]

I just got a iPhone 4 Orange France used (it was REALLY cheap). I took it to a mobile shop so they can de-block it so it can accept my SIM card. He said that there are two ways: a cheaper and a more expensive way to de-block it. The iOS is 4.3.3, so he said he'll be able to do the cheaper way if I don't update the iOS ever. I said it' OK and he de-blocked it. But he told me he has a problem that it keeps telling him "no service" or it shows very low signal and doesn't even display the name of the operator. He told me to bring it home and try experimenting, he didn't ask for money and he said if I couldn't figure anything out on my own that I bring it there for further inspection.

So that's why I'm here. Is there a way to fix this? When I have no service or it's "low signal" I can't call or text. Is there a way to fix this? Please tell me in detail what do I have to do. If it requires jailbreak, tell me in detail what do I do after the jailbreak (Is jailbreak even possible without updating the iOS?).

Thanks in advance.

 

[willerz2]

Once a phone is blacklisted and the ESN/IMEI is tainted, you can't un-taint it. Regardless of whether the device is jailbroken or not, a blocked/stolen/flagged device will not run as intended compared to a clean device. The only solution would be to buy a clean device rather than buying stolen/lost devices and use it on an official carrier rather than trying to get it working with shady methods. Old backdoor methods have been patched by 9 out of 10 carriers worldwide, and are completely patched in North America, Latin America, and Europe.