iphone 4s "sim failure" then "invalid sim" frequently
Hi,
I purchased my Iphone 4s nov/2011 and in the last 3-4 weeks i am facing frequent errors of "SIM FAILURE" then it goes to "INVALID SIM".
i must turn off the on my phone each time it appears.
sometimes the intervals between errors is few minutes and sometimes it can take up to 3-4 hours.
i replaced my sim card twice at the network provider but the errors remain.
i switched with another ihopne the sime card - the error appears on my phone again and on the other phone the sim works good.
checked the settings but couldnt find and diferences with my son's iphone(which we bought the same day at the same store).
any one with any information will be appreciated.
thanks
yjsitbon
iPhone 4S, iOS 5.0.1