I'm using a SoftBank Japanese iPhone 7 in the US. Roaming for voice and data is free as long as Sprint’s network is used. As per Softbank’s instructions, data roaming should be set to off while 4G voice and data should be enabled, and network selection should be set to automatic. The phone prioritizes Sprint when selecting networks.
However, while in a Sprint dead zone, I noticed that the phone connected to T-Mobile. No “4G” indicator followed “T-Mobile” in the status bar. I forced the phone back on to Sprint. Yet when I looked at my data usage, 126 KB of roaming data had been accrued.
How is this possible when roaming data is set to off? After searching Google, I read that others have experienced similar circumstances with multiple carriers. Yet I cannot find a reason as to why. Shouldn’t “data roaming off” mean “data roaming off”?
However, while in a Sprint dead zone, I noticed that the phone connected to T-Mobile. No “4G” indicator followed “T-Mobile” in the status bar. I forced the phone back on to Sprint. Yet when I looked at my data usage, 126 KB of roaming data had been accrued.
How is this possible when roaming data is set to off? After searching Google, I read that others have experienced similar circumstances with multiple carriers. Yet I cannot find a reason as to why. Shouldn’t “data roaming off” mean “data roaming off”?