There are two issues here,
When using Teams in both PC and mobile device, when a new notification comes for a message, call or any other notification activated activity, I get the notification on both desktop app and mobile app at the same time.
This is when i am using Teams on desktop app. Let say I had a teams conversation on the desktop app. Then after sometime I am logging into the Teams mobile app from phone. Then I am getting all the messages I have already attended to from Desktop app. This is really annoying.