I am currently visiting Ireland. I have a iPhone 6plus. I have followed Telstra webpage instructions and have data roaming OFF and mobile data OFF. The phone is showing very small amounts of data usage. I have contacted Telstra but other than trying to sell my Day Pass or turn off data at their end they have no idea.
I read a thread about what sounds like the same issue on Whirlpool a while back but I can’t seem to find the thread now, but it’s not completely unknown for this to happen.
Evidently there are a few low level functions which can cause this but I’d be disputing the charges with Telstra if you get a bill for them.
This is a common issue. The only way to ensure you don’t get charged anything at all, is to take your SIM out of your phone.
Whether it’s a fault with the iphone somehow using a minuscule amount of data when it’s not meant to be using any, or a fault with the Telstra Billing System, I can’t say. But you should certainly dispute the charges if you wish to, and take it as far as the TIO if necessary.
I can’t explain the data, but put simply if you have international roaming not activated with Telstra, they can’t charge you anything.
FYI a couple of the Telstra plans offer roaming data
Mine does! But it’s only 2gb