Unfortunately there is no "off" option to totally turn off all notifications coming out of TDX for a person. If they typically receive notifications only because a group they are in is being contacted as a group, then you could configure their group-level notification setting to not be notified when the group is contacted. However this does not turn off individual notifications to them from TDX.
It would make a great enhancement idea if you wanted to submit that specifically.
Sr Support Consultant, CS