I updated my BB Z10 to OS 10.3 and it disabled T-Mobile's WIFI Calling app. Called T-Mobile BB support and I am getting the run around. T-Mobile says they have not gotten the OS 10.3 update from Blackberry and do not know when they will get it. Or, Blackberry is adding WIFI calling to their OS but have no idea when it will be available. I wish BB would stop disabling that app when a new OS comes out.