Can't actually find a reference to the APN in my phone's setup. I guess OnePlus do things differently. It's different Sims in the 2 devices. Routers APN is 3internet.@Oft1950 Can I just dig into your phone vs B535 comparison a little more.
a) Are you using the same sim in both devices, or are they two seperate sims/contracts
b) Did you try different APNs? If not -- Do you happen to know what APN is configured on your phone when it seems to work - is it 3Internet or three.co.uk? How about the router?