WiFi on longer routes

[BlackDiamond]

With smart phones, you may not be explicitly browsing, but your background services may be connecting to your servers. Think email, it will be checking for new mail periodically. So best to shut off cell service if you think you might have an issue.

I have an old AT&T plan, which evidently does not include CA and Mex roaming anymore. On some recent cruises I had to manipulate things accordingly.
Normally I get a text when it roams, and I quickly shut if off, and haven't been caught out by any charges.

You could put the phone in Airplane mode which should still allow you to use WiFi if it is available.

 

[lstone19]

I got nailed for Verizon international day charge as I slept near El Paso on the SL/TE. At some point we were a few hundred yards on the US side of the border, and my phone was asleep the entire time so I place no calls, sent no messages and did no web browsing through a Mexican cell tower. So if you have an international service, be sure to explicitly disable it before getting close to the border. (The charge seemed to have kicked in an hour or two east of El Paso while I was still asleep and the train was much farther from the border than we were in El Paso itself (west bound), so probably it's a good idea to disable it the night before at bed time.)

Being near the border in a remote area of the U.S. can cause a tower across the border to be what gets picked up. Earlier this year, we were driving on the Lake Ontario State Parkway west of Rochester when I received a T-Mobile "Welcome to Canada" text message meaning my phone had picked up a Canadian tower in one of the Canadian cities east of Toronto across Lake Ontario. Not a lot in that part of NY so not a lot of close towers.

 

[Willbridge]

Being near the border in a remote area of the U.S. can cause a tower across the border to be what gets picked up. Earlier this year, we were driving on the Lake Ontario State Parkway west of Rochester when I received a T-Mobile "Welcome to Canada" text message meaning my phone had picked up a Canadian tower in one of the Canadian cities east of Toronto across Lake Ontario. Not a lot in that part of NY so not a lot of close towers.

My Army colleague who lives in Ferndale, WA (long ago a stop on the SEA <> VAC mail train) was picking up cell service from British Columbia at home. He's an electrical engineer, so he understood how that was happening, and eventually worked out a concession from his carrier. Then they were bought out and he had to repeat the talk with people in Atlanta who were not up on geography. Eventually things were worked out.

British Columbia from Ferndale.