Had the exact same problem with my S3 as well. I'll be in an area with full 3G coverage, but the phone doesn't connect to it, just displaying 5 bars of phone signal but no data connection. To get it back I have to turn flight mode on & off, which then instantly gets the H+ connection back online. Assumed it was a faulty handset issue with the S3, but now the S4 also does it I assume it is just normal. Anyone have same issue?