iPhone 4S dropping network and data at random

Just to clarify it again for everyone:

If your network drops and you get constantly Invalid SIM, SIM failure message or your cell reception bars drop without any reason:

1. Try to restore to version 9A406 (http://support.apple.com/kb/TS4148)
2. If this does not help (it helps only to some phones and some SIM cards - I want to make this clear, I am one of those frustrated) try to get a 128K SIM card from your provider (http://www.ehow.com/info_12168797_64-k-sim-card-vs-128-k-sim.html)
3. If this does not help or your provider doesn't have/support 128K SIM cards (again its my case and there are people here where 128K SIM did not help) return your phone and get a new one, or wait for 5.1. to see if this issue gets fixed.

Note:

• In my case 9A406 is totally unusable, network drops and SIM card issues were so several that I had to restore my phone back to 9A405 so I can at least use it occassionaly. At this time it is pretty expensive iPod docked in a docking stations and I am back by my older BlackBerry device.
• Try to call Apple support, if you followed those steps above it will not help 🙂, but it might decrease your frustration for a while. Apple Support does not know when iOS 5.1. will be released - they get the notification exactly at the same time like its published to web (iOS releases are done by other Apple departments and its a common practice).
• There are as well reported cases where exchange of iPhone did not help - it might be that those guys did get an iPhone from a same batch, or its a combination of SIM&Phone errors. In that case if this issue would not be resolved within 5.1. get your money back and get some other phone - there are plenty of enough cool ones on a market now.

Thanks man! I did exactely all steps you suggested, the network is still dropping. Gonna have it exchanged hopefully. Still dont know what is Apple waiting for, the phone has been out for more then 3 moths and not a single word about this issue was given by Apple...

It didnt work, network still dropping. The phone s going to servise ASAP. Thanks anyway!

sorry to hear that...

My phone is working perfectly.. I just throw my mobile in dog **** and got a samsung galaxy s2....

Do try my fix... It works...

Hi tamerlan...,

I'ts not a coincidence. The build work or it doesn't. If it works in your phone, then that's it. I only restored my firmware once, and the "No Sim" and "No Service" problem hasn't resurfaced. Been running on this for 7 days now.

http://iphone-and-i.blogspot.com/2011/12/fixing-iphone-4s-signal-problem.html

Hi 8Honza,

If you go and check your firmware version in your phone, what does it say now? (Settings > General > About > Version). I've tried to outline some verification steps in the link below.

http://iphone-and-i.blogspot.com/2011/12/fixing-iphone-4s-signal-problem.html

scott

Hi Scott,

it says 5.0.1. (9A406). I aleady did restore , it was working all right for some time but then it dropped again and I still loose signal... 😟

Scott, I have read your step-by-step tutorial, seems that you know what you talking about. Do you have any clue what might solve my problem? Since my current version is 9A406, it is useless to do another restore, isnt it?

Hi Scott,

Very good Step-by-Step tutorial, unfortunelly it did not work for me 😟 I'm using 5.0.1 (9A406) with iPhone model MD257E. I have tried everything I read in this forum and still have the Invalid SIM or SIM Error issue, I think the only solution for me is to be patient and wait for an uptade or exchange my phone with the carrier company.

Thanks for the tutorial, very nicely done.

Francisco

Hi Francisco,

I have exactely the same problem as you. I will definitely NOT wait until Apple release an update, I bought the phone to make calls and send texts! I m pretty upset! All I do nowadays is just turning on and off my phone over and over to be able as least make one call or send a single message! Moreover, I cant use 3G either!

I know, is really annoying and if is wasn't that I did transfer my phone calls to another mobile I have from work, believe me I will exchange my phone right away. I use data instead SMS, so I can manage between wi-fi or restarting my iPhone. Another reason why I haven't return my phone is because they will probably give me a refurbished one. I know is a stupid reason, because it is a working phone, but I think is part of my neurotic behavior. 😝

Hi 8Honza - it's probably a good idea to replace your phone but then when you do, try to have your phone activated right there in the store. That way you'll know right away if the replacement is good or also problematic. My iPhone 4S showed the "No Sim" problem on the first day of activation, which I did at home. I did try to have my phone repalced as well but guess what, they ran out of stocks. Did you manually update to 9A406 or did your phone come with than version installed already?

Well, basically we both have now pretty expensive iPod touch :/

Hola Francisco. Did your phone come with the 9A406 already or did you do manual upgrade?

In deed 😢