It was great until I tried to use the app to see & pay my bill. Even though T-Mobile used it 7 times to confirm my order, my email doesn't match their records. Because I don't know the PIN because I didn't make it, it can't verify me. There are people who have had the same issue for months asking for help on T-Mobile website. While it's "not secure" for me to see the bill before paying it, there's absolutely no problem with giving them my credit card info as a guest-no verification needed.