I have to chuckle because you're blaming T-Mobile for something that is YOUR responsibility. Set up a recurring notification if you need to.
I always received a notice from T-mobile several days prior to expiration and had no reason to think this would not continue. It has, except for that month, so it WAS an error by T-mobile!
However, to avoid this happening in the future, I did set up a notice in my Calendar app to recur every 30 days.
Hey there! You can setup auto refills and other reminders.
Our apologies for any confusion or inconvenience.