I spent many hours trying to find this info online. Finally, I spoke to a T-Mobile rep who helped me. This is where you go to get the info: https://login.northlane.com

This is the site to check your balances. It is no where to be found on T-Mobile.

https://login.northlane.com/ this link worked for me thanks.

T mobile totally sucks This should not take this much time! I believe it is deliberate on T mobile's side to make it this difficult

The North Lane site won't let me create a login (cannot get past the Captcha).

Anybody else have that problem?

AND I GET THIS

The connection for this site is not secure

login.northlane.com sent an invalid response.

• Try running Windows Network Diagnostics.

ERR_SSL_PROTOCOL_ERROR

Never have I ever had such difficulty getting on a site

Also can’t get on this site. Ridiculous

Just dial this number 1-800-439-9568
1 for English > enter card number and it will give you your balance. 
You can also set up your pin after it gives you your balance. 

The number 800-439-9568 given by the last person WORKS!! It will give the balance & also a choice for the individual transactions you’ve made on the card.

I waited and had to call twice  finally after 4 months I called and received them a couple weeks later.

Customer service says you can check your debit card balance by texting the word “Bal” to #7283