Well I finally went to the Apple Store/Genius Bar in Barcelona and was told that:
1 - I should never do a DFU on my own because if it hadn't worked out or I had messed up the iphone in any way that the warranty would no longer cover my phone.
2 - That any time I have a problem I should contact Apple Support or go the Genius Bar
3 - He looked at my phone and determined that the problem I had was due to my sim card: Movistar (previously known as Telefónica in Spain) sent out a batch of sim cards that were not micro-sims but rather "cut outs" of the big sim cards to make them the size of micro sims. He said some people had no problems with it, others did from day one and others would suddenly start having problems (my case).
So I went to get a new micro sim, for which I had to pay 6€. I then called Movistar and they must know about this "cut out" micro sim because they credited my account with the 6€ without having to explain much or give any type of serial number.
I did that last Thursday. Since then I've only had 1 dropped call, versus the mulltiple ones I used to have every day. I will report back after a week with results.
I went to the genius bar and was told to return the phone to sprint if it was within my 14 day trial period. They could offer no suggestions to correct the problem. I was really surprised to hear someone from apple tell me to return their product for another phone all together. Extremely disappointing.
That's my update.
After talking to Apple store folks they agreed to change my phone to a new one. They also suggested to set it up as a completely new phone and not go with restore option when initializing for the first time in iTunes. That's what I've done and in addition I've also replaced SIM card with AT&T.
Result - it's about 2 weeks and it's OK so far. No dropped calls. No issues with switching in between phone/speaker/Bluetooth as before.
I see I'm not the only suffering from this afterall. I have used iPhone 3G, 4 and now 4S. And the 4S is the worst in terms of battery life and call drops (which never existed with the previous models). I use STC in Saudi Arabia and the dropped calls have reached 50% after four months of using my iPhone. I can't wait for the iPhone 5 to get rid of this trash.
I'm now alright with my iPhone 4S 32GB. Not fully satisfied because my solutions narrow down the features of the phone - but its acceptable.
What i did:
- Called apple to reset my account registration profile on their servers
- Restored the iPhone and thus downloading the latest build of iOS
- Shut off every push-email-service and set it to manual.
- Shut off as many push notification services as possible coming from 3rd party apps.
- Normal battery life up to 3 days when not working much on the phone
- No call drops anymore
- Speech quality is not perfect but seems to be much better now
Give it a try!
I'm on AT&T and my 4s drops far more calls than my 3G ever did. It's super annoying. The phone is only really good for very short conversations and texting.
On the plus side, I've actually taken down the number of voice minutes I buy substantially, as I can't have phone calls long enough to use them up. . . .
I have been suffering a similar problem as Haiponers, in my case in Bilbao, Spain, carrier Movistar.
I have gone through 2 iphones (bought the first one directly from Apple, got the second one through Applecare), and many resets. And have tried 3 microsims from Movistar (6€ every new microsim), to no definitive solution. I tried the first and second microsims on my first iphone, the second and third microsims on my new iphone. I even bought the microsims in different retail stores, trying to avoid the wrongful batch problem.
It's just a matter of luck now. I have noticed that the iphone randomly loses all connection once in a while (say a dozen times a day). It goes from service to No Service, then Searching, then finally recovers the connection with the carrier. If this happens during a phone call, the call is dropped. It's chance, it's random, and it's annoying. No problem for data services, connection is back in about 30 second, but it's very frustrating for phone calls, specially when talking to clients.
I have even thought about purchasing a phone for making calls, and leave the iphone for the internet. But then, I'd have a very expensive wifi-3G iPod Touch. And two devices on my hands.
I know it's most probably a carrier issue, but calling Movistar has no use whatsoever, the people on its call center has no idea what I'm talking about. And switching the carrier is not on my mind now, due to my business needs.
Very frustrating overall.
Thanks for listening anyway. Cheers, everybody.
So here is the latest. After changing the microsim i still had multiple dropped calls. Not as many as before but still a large number. I went back to the genius bar and they gave me a new phone. After 2 weeks same problem. Constant dropped calls. I went back to the genius bar again. I was told to do a reset and not use the copy i had in my icloud. That is, use the iphone "from scratch". That did not fix the problem. So I went back to the genius bar. And they gave me a another new iphone. I'm still dropping calls now worse than ever. The guy at the genius bar told me it was a problem with all carriers because the 4S is so advanced and their systems can't handle this phone. I could keep going back and keep getting new terminals but at this point it does not make a difference. I asked the genius the same question: if its a problem with the carrier why give me a new phone. His answer: maybe this time you will get lucky...I am so frustrated. I miss my 3GS. I love the speed and the features if the 4S but with this call issue it basically kills the whole point of a smart phone since the phone feature is useless. I think I will switch to the Samsung.
It is not a network problem, it is totally device defect. I have bought a new 4s in Saudi Arabia. The call drops many times during the conversation and i receive missed call.Same location, same network galaxy s2 does not have any problem. So, what can i do now? apple should replace my phone!!totally disappointed.i bought it for my wife and she wants galaxy now!!