I was anyways working on describing the new Nexus 6p and reviewing every detail. But I have recently bumped into an annoying issue which seems to be also affecting our fellow Nexus 6P users across the globe. I came across an article describing the problem in Austrailia with a particular network provider.
It is very irritating to find your super powerful phone which supposedly Premium but fails to connect and use cellular data.
If you are on a Wi Fi network and suddenly step out its range it does not seamlessly start using the Cellular Data. It may very well appear like the issue where your phone has suddenly slipped into a Roaming zone and you had switched off the Roaming cellular Data option.
The main solution would be to restart your phone or ensure you are disconnecting from the GSM network and re-connecting. I painfully spent the first few days restarting my phone again and again. To add to my pain it never worked in one restart.
I found something really simple & easy to achieve the same and it would be going into Airplane Mode for 5 seconds and returning back to the active mode. This move facilitates the re-connection of the GSM network.
BTW Google are already aware of the issue and are working on delivering an OTA update with the fix after testing is complete.