T-Mobile monthly 4G question?

[AzNsLoBOi922]

I'm thinking about getting the 15 dollar a month, 10 cents/min and unlimited texting. My question is for the 10 cents/ min. Do I pay for whatever I use or do I have to buy a card every month? Also, do those cards expire every month?

 

[SingleWhiteMan]

Get a Net20 or Tracfone instead.