I have never managed to connect to BT hotspots from my iPhone 5. After an hour on the phone with BT today, checking my settings and trying various things and eventually giving up, BT told me there is an issue in using BT hotspots from IOS 9.2 and 9.3. They sent me an Apple link to try - faced yet to attempt this!! Anyone tried it - before I totally wreck my phone?
I use an iPhone 5s with iOS 9.3. On my old iPhone 3G I at first could not log in to BT with FON, and BT themselves were no help at all. Then I discovered that right at the top of the screen one gets to when one starts trying to connect and register there is a tiny button that leads to another place where I was able to complete the process. Whether that would work with 9.3 I don't know. But BT gave you misleading info. I have now (on my new phone with 9.3) installed the BT app and.have not the slightest difficulty with BT wi-fi.