I travel to the US frequently and I never dial/answer voice calls or send SMS/MMS messages while there. "Auto-download MMS when roaming" is also disabled.
I've always had data roaming disabled on my phone but in the past this didn't stop me from getting roaming charges sometimes but they were always small amounts (like 0.070MB or 0.050MB) and I would get the $5 US data roaming charge.
As a result, I decided to start manually disabling mobile data before leaving Canada while the service provider banner still says Koodo, using strictly WiFi while in the US, and then only re-enable mobile data once the service provider banner says Koodo when back in Canada.
This worked fine for months, then suddenly starting in July, I started getting text messages after returning to Canada saying "Welcome back to Canada! Check your total roaming usage at koodo.com/selfserve" and when I check Self Serve it says I'm being charged $5 for US Data Roaming as a result of 0.001MB (1KB) usage of data... How?
I just got off the phone with a rep to have this corrected for a charge in September. He said he couldn't pinpoint what generated the data, but it was possibly a "notification". As always, no SMS/MMS messages were sent while roaming and none were received on this specific trip either, strangely not even the standard Koodo welcome to the USA messages.
Back in July the rep "claimed" this was a known issue, but today's rep did not have any idea of any roaming billing issues and it was like pulling teeth to have it corrected. He made it sound like he was doing me a huge favour as a result of my own mistake.
Something is wrong with your system in regards to tracking US data roaming and it needs to get fixed ASAP because I'm sick of calling in for billing corrections.