After connecting my S10+ by USB 2 to a W10 computer with USB tethering on to download an email, I received within 2..3 min. a SMS from cockpit, that I have used up 90% of my 3GB and shortly after a SMS that 100% is used. The SMS time stamps are 1 min. different. On the phone the total mobile data usage was given as 177MB and for Mobile Hotspot and Tethering 139MB. Checking the Swisscom Hotline was useless ("the data are used and basta") and the Samsung Hotline indicated a difference between the phone and provider measurements within a few percent are normal, but could not think of such a difference.. I would be grateful of a hint!