Finally gotten around to upgrading the wife's iPhone 4 to the latest iOS but now she's getting an intermittent issue with SMS.

The messages don't go to the correct person, I.e. an SMS she sends to me, actually arrives on her sisters phone.

It's not happening all the time and it's not limited to certain contacts, it's completly random.

Anyone seen or heard of this before, dealing with 3 tech support for 2.5 hrs was painful today.

That is bizarre, sorry I haven't seen that before. Good luck.

Is there an Apple store nearby. If so pop in one of those and get them to help you. I've heard they are meant to be really good.

Try and check all the numbers are stored correctly .

Same thing happened to me once and it just merged some numbers with others and swapped the rest around