I purchased the 4S on the day it came out and haven't had any issues at all to this date until earlier this evening. I was on the phone and all of the call failed. I looked at my service bar and it was showing I had 4/5 bars. Then my service will cut off for about 30-45 minutes where I should clearly have full service. It also does this with the voicemail. I have no idea what's going on.