I cannot update!!

I can’t seem to get xfinity mobile app to update my debit card with the same card # just different exp date and security pin! XF you need to get your developers or whoever is in charge allow customers to update their cards! I have no way of paying my XF mobile bill the way things are right now! Please comcast respond to this and let me know how you guys want me to pay my bill! I look forward to hearing from you guys!!