Phone goes to roaming when switching from 4G to 2/3G on ice+ in Norway

[erik_paladin]

It seems that the network names for ice+ in Norway are different between 4G and 2/3G.
For 4G it's "ice+" and for 2/3G it's just "ice".
So when the phone switches to the "ice" network, it goes to roaming mode, even though it's practically on the same network. This can be reproduced by simply changing the preffered network type in the Settings menu for the SIM.
Maybe this can be fixed in a future update, so we don't have to disable roaming notifications?

[tor_bjornebole2]

I'm in Norway too (and use ice), and from what I understand, ice have both their own network (ice+) and borrow from Telia where needed. That means it would be roaming in Telia's network when their own isn't available.
I talked with ice support about this a year back since it defaulted to Telia when I needed ice+ to take advantage of their 1000 GB data package offer. They said it depended on the relative signal strength of the two networks. It would sometimes default to the strongest one.
This happened to me using a Pixel phone. I've not had a chance to try it with the zenfone yet.

[Gustav_ASUS]

Taking the detailed answer (thanks for that!) from @tor.bjornebole2 into account, it's very possible that this is a carrier-based behavior that we really can't control from our end.
With that said however, I'll pass your question on and see if I can get a better explanation from our network team.