cannot make or receive calls

Dear leewing,
i was ironically ecstatic to see someone has the exact same problem as me... it's been a few months since i bought my 4s, and it happend a week after i bought it! i set an alarm on siri and the next morning when i woke up, it was dead like you described... i searched the forums and a few other people (maybe because i bought it early on) were talking about it. they all were complaining about how siri is causing the problem (which i'm pretty sure was because people with iphone 4 haven't updated their phones to **** ios5) and as a solution, were saying that you have to turn off siri and restore. i did, and it went away. today (after keeping siri off for these 5 or 6 months) it happened again! can't describe how frustrated i am to know that it wasn't siri... or at least, not JUST siri... but turning off 3g and cellular data, and turning them on again solved it... heavily dissapointed apple! just wanted to let you know i have the same problem... now i don't know if upgrading to ios 5.1 solves it or not... any ideas on that?

Hi MiFTiL,

I don't know if this helps, but since I updated to ios 5.1 I haven't had this problem. It seems that the update has worked, but I can't say for sure of course. Hope this helps!!!

Hi MiFTiL, aisling27,

Yeah, i do think iOS 5.1 has resolved the problem.

& i do noticed (quite a lot of times) that when the signal got wrong,

it will automatically "recover" itself, either the Cellular Data & 3G is ON/OFF.

I hope it works the same as yours too...

I'm having this problem on my 3GS on 5.0.1. I can't even restore it or update the firmware!!!