Is it possible to repair the network hardware in an iPhone 3G?

i will get mad, please help what is the problem with my iphone

• recently i updated my iphone 3gs 4.2.1(which was already jailbreaked) to ios 5. since it didnt work at all because it got locked so I tried jailbreaking ios 5 using redsn0w, but didn’t work for me. Then i again installed the ios 4.2.1 tried to jail break it but still didnt work, no network and all those stuff so i went to the repair shop. there they installed ios 4.2.1 jail breaked but doesnt detect the network, nor carrier, doesn’t show the carrier nor the iccid .recently after i brought back my mobile to home, i discovered that when i switch the airplane mode on and then to off, then my iphone detects the carrier, shows the iccid, searches for network a while but at last shows network not available, no service, but still shows the carrier and iccid until i restart my iphone, and again airplane mode on, then to off..... what is the problem? is it the software or hardware problem? In the repair shop, the repair person was saying that “may be it is a hardware problem”

• Answer:

  It sounds like you may have lost the connection to your wireless service provider or maybe your phone can't handle the update/upgrade. Did you buy your phone at a store...if so, they can assist you. For example, I bought my smart phone at a Bell Canada store so when I had a problem with it, I took it back to the store. Or can you call a customer service number for whoever made your phone? I took my computer in to a repair shop and they had no idea what they were doing...best to take it back to the store.