Cellular data is off but cell phone uses data especially when rebooting

[Android Central Question]

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!

 

[Mooncatt]

What makes you think data is being used? I.e. Are you looking at a meter on the phone, actually being charged for it by the carrier, or something else?

 

[Gaggz7]

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.

 

[Mooncatt]

That doesn't make much sense, unless you're being charged for MMS messages (they use data).

Have you tried working with your carrier to see if you can disable mobile data on the account itself? That way it wouldn't matter what the phone does.

 

[Javier P]

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.

Welcome to the forums. See this thread, it's quite old but the last replies could help you.

https://forums.androidcentral.com/showthread.php?t=361183

Do you have Developer Options enabled? If so make sure that 'mobile data always active' is switched off.

You could also disable roaming in your mobile data/SIM card settings and see if it works.