@lakesadam wrote: Appreciate your help, well have a look when it does it again. I've had this phone for about two years now, strange it's only doing it since switching to BT. Will keep you posted.
Further to my last post...
I've discovered a flaw in the S5 network notification.
I don't want to go into detail, as this will only create confusion, but there's a condition on the S5 where the network notification disappears altogether. At least you have an indication, on your phone.
It's possible that your data connection is still there, but the only real indication is to go to Settings > About > and look at Status. You will find the "About" icon eventually!
Must admit, I had to "cheat" before replying to you by doing a Google search about the exclamation mark symbol on the Nexus.
It's a known problem unique to the Nexus, but why should it just have appeared with BT?