Easy Roam triggered without any usage

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We just returned from the US and noticed that my wife's phone had 5 days of Easy Roam charges even though data roaming was turned off on her phone. My account showed no airtime and no data usage for those days. One of the charges I've resolved and was attributed to my wife sending a SMS message which would trigger Easy Roam but the other 4 days are a mystery (paying $7 to send 1 SMS message - ouch!)

In an online chat with Telus I was told that there was a tiny amount of data usage on each of those 4 days. So tiny that it rounded to 0.00 MB of data on my usage page. How is that even possible with data roaming turned off? Even if data roaming was somehow accidentally turned on and then off again there would be much more data usage than 0.001 MB. There must be some bugs in the way phones are connecting to the towers.

Telus has credited me for the 4 days of Easy Roam so I'm not on the hook for the charges but from now on when I'm outside of Canada I'm putting her phone in airplane mode and just turning on WiFi. My daughter's phone was set like that and she had no roaming charges. I had my phone using Easy Roam was running a hotspot for my wife and daughter whenever they needed data.

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Data can be consumed when a phone is restarted, before the data roaming acknowledgement occurs. Was the phone turned off when not in use such as overnight?

It seems data can be used when the phone connects to a 2G  network.

Android phons  seem more often to use these tiny amounts of data than do iPhones. What devices were you using?

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All Android phones in my house. At no time was my wife's Nexus 6P powered off or restarted. She keeps her phone on when charging overnight because my oldest daughter is away for 1st year University and with the time zone difference we never know when she might need to contact us.

We had LTE every time we had a signal. It's possible on the outskirts where the signal was sketchy it may have fallen back to 3G but we were only in that area on 1 of days.