cell phone consumes mobile data when mobile data is off, especially when rebooting

[Gaggz]

Hi. I have Samsung S9 plus and sometimes use it with a cellphone connection from overseas. While on international roaming, it costs me lots even if I use few kb of data, hence I turned the cellphone mobile data off (WiFi is on). I noticed on Samsung Galaxy S9 plus that even when mobile data data is off , the cell phone uses very little data especially when rebooting. After rebooting it does not consume cell data. On the other hand, I have Google Nexus 6P and it NEVER uses mobile data when mobile data is turned off, even while rebooting. I was wondering why the S9 plus "steals" some data especially when rebooting and Nexus 6P does not. Also, would appreicate an recommendation on any other Google or Samsung phone that will never use or steal data when mobile data is turned off, even while its rebooting. Thank you!

 

[bcrichster]

I would "assume" it's likely a service location check, like a ping to see which towers you're closest to and check Samsung servers for updates. I don't really use Sammy devices so this is simply speculation

 

[Gaggz]

I have tried this in separate bill cycles using each mentioned device. There is a data usage, broken down into time and date which coincided around time of S9 plus device reboot. I am billed a good amount for even small data usage. Such bills never came up when sim card was placed in Nexus 6p (standby or reboot). Hence I the conclusion.

 

[kate]

it costs me lots even if I use few kb of data, hence I turned the cellphone mobile data off (WiFi is on)

Did you only turn mobile data off, or turn Airplane Mode on?

If you just had mobile data off I'd try also enabling Airplane Mode when you reboot, that might keep data off when it restarts.

 

[mikedt]

"hence I turned the cellphone mobile data off"

In addition to that, check the International Data Roaming setting is OFF as well.

 

[Gaggz]

Thank you everyone for your help!

 

[James_Watson]

Thanks for your information. I would like to check my device, too.
But would you like to tell me how to check whether it will use mobile data while rebooting? Thank you in advance.