This is something weird that I've discovered too. I am now on T-Mobile (from AT&T) and there are all sorts of T-Mobile features that may or may not work depend

This is something weird that I've discovered too. I am now on T-Mobile (from AT&T) and there are all sorts of T-Mobile features that may or may not work depending on what SIM card you have in your phone. And if they don't work you have to get a new SIM card (that is not guaranteed not to disable other features.) What!? That seems to be the weirdest thing ever. What is going on?