Once you have tjmaxx mastercard login there are multiple things that can be done:-
First you have manage your account, payment, balance etc.
Second easily make payments.
Third get 12 months bank statement at your mail.
Fourth is setting reminder for various payment and balance updates.
Fifth change your address, phone number and other information easily.

The short and simple answer for update payment spotify from app is no you cannot update spotify payment method from application of spotify, it can only be modified from website. The same Account page where you can view your basic account information, like your username and associated email address, also allows you to examine this data.