Every time you lose service, a much faster way to get service is to turn airplane mode on and off. Also, have you updated your iPhone to the latest software? If you haven't you should do it. And if all this does not work, try restoring your iPhone and get it swapped out at the genius bar. But don't tell them you dropped it. They have no way to find out! Also un-jail break your phone before you take it there.

The problem is a loose cable. Open the iPhone through iFixit steps and reconnect the cables and you are fine.

I have fixed a lot of phones this way with the same problem.

Depending on your current firmware, updates also update the radio's baseband. I was having the same problem for a while until i did a full update. Carriers will always change their network configurations to increase their data speed. Also before you do so, back up your files and do a complete reset all settings from settings/general/reset all settings. It will take about an hour. This will erase any registry file value that could be causing the issue. Hope this helps.

When you dropped your phone i think you have damaged your mother board. I had an incident with my iPhone 3G and now it will only pick up 3G signal. Take it to an Apple store and see if they will replace it for you. I don't think there would a DIY solution for this.

I had the same problem and had to replace the antenna and antenna flex.

It takes a lot of patience to do it, but it works fine now!

total cost: €20 (or 30 dollar something)

This may sound strange, but I believe if the SIM isn't seated properly this can occur also. I think it's much more likely the antenna is damaged though, the flex cable is delicate.

Hate to state the obvious, but have you tried a reboot?

My phone is having the same problem, i lose service all the time and its in the open where i always get service. i try to reboot and it doesnt work, reset the network settings and it doesn't work, turn it on airplane mode and it doesn't work. and then sometimes it doesn't lose service for hours. what do i do?

I have exactly the same problem with CAM. i ever dropped my iPhone :- and then the problem happened.

I have the seame problem of "No Service"...... It has been sent to a repair center and they have said that the charger socket is damaged and so the repair is not covered by warranty...... There is no problem with charging or conecting to iTunes, is it possible for a damaged charging socket to cause "No Service"??

If i was u just replace the antenna or put a foil on it that covers the battery and the signal well give it a big boost and it shouldnt be cut off anymore. That's what did and it's works good :)