iPhone 4S drops 3G, have to restart phone to get it back

My 4S was replaced 4days ago. The new 4S is working properly no problems with phone calls (no phone network drops) and no battery problems (battery charge lasts over 10 hrs now). Sim pin is on for testing purposes (4days).

My SIM PIN has been on 3.5 days and there has not been any problems on phone calls on my replacement iPhone 4S (I got from Apple on Wednesday). HOwever, I would like to turn off this sim pin setting because it is not clear whether the sim pin on -option is mandatory for higher security of my iPhone4S and there might be still some bug related to iOS 5 causing undetectable drops from 3G phone network.

Thank you antti51 for this tip.

My new 4S has been working properly now since I turned the PIN lock off.

No flat lines on 3G anymore, and it properly changes between 3G and GPRS. These are the options we have were I live.

Now to wait for the IOS 5.1 update.

Follow-up on my own post.

For me it does not help to disable PIN..... Still have issues with that the phone looses signal completely and outgoing calls fail (in areas with good coverage).

Hope this is a software error that will be fixed in 5.0.1!

I have the same issue

Disabling SIM PIN doesnt fix it. Apple support have suggested doing a restore. Do you think its worth a try or get a replacement?

Think i may have figured it out, at least for me (and killed 2 birds with one stone re: battery life)

The 4S now has multitasking. If you double click the home button you can see all the running apps. Holding them down shows a red minus which allows you to kill them. When I turned them all off, bar the base IOS5 apps the problem went away (same thing would happen if you restart the phone)

So it will be a rogue app that is causing this which isnt being turned off. Guess only way to work out which one is to try them all but i havent got time

On a side note this also increases battery life, I found i has something like 30 odd apps running so no wonder my batter was draining so fast

I seem to have similar problem with losing 3G on a 3GS working on Orange PL network. Disabling SIM PIN doesn't work on contract SIM cards. Looks like a firmware issue to me.

Apparently I had spoken too soon before when I thought the problem had fixed itself. I resisted for a while, but finally performed a full restore and set up as a new phone (NOT FROM BACKUP). It's been a few days, and I THINK it's working. I haven't lost the 3G signal once, and the battery life has improved as well. I'll report back in a few days to confirm.

Setting up as a new phone will force you to lose your old text messages, high scores on games, etc. I was irritated at first, but I'm over it; there are worse things in life. Assuming you have your contacts/calendars synced through an exchange server or icloud, I think there shouldn't be any problems there.

Did you try killing all background apps? As above?

No, not yet. The problem happens occasionally so I'll try it next time I see it. Still, I don't think that's a real fix, just a temporary remedy.

I agree but my guess is there are apps that cant/dont manage the CommCenter stuff well with multi-tasking. In which case either Apple fixes apps being able to do that or we find the apps causing the issues and report it to the vendors

Same issue with me here in Germany. I even brought my wifes 3GS out with me to compare and the 4S drops to "No Service" while the 3GS is totally fine. Both phones on the same network.(Telkom)

The only way to get the network back once in "No Service" is to shut it off and turn it back on again.

So far I've tried:

3 new SIM cards

Resetting Network

Resetting Phone

Total Restore

Now I've taken the phone back to my carrier, and they are sending me a new one. We'll see if that helps.

So far, very dissappointed with the iPhone 4S.

Repairee: Did you try it without doing a restore from backup?

What I mean is did you test the 4S if setting up as new device? Did you have the problem then as well? If so, I would say it is more likely a hardware error.

I set it up as a new device. When that didn't work, Applecare told me to take it back and get a new phone. ie: hardware issue.

Ok, interresting! It would be great if you could report back here after you recieve the new device if you have the same issues!

(Hope that 5.0.1 will not have been released by then to easier know and verify that it is a hardware error)