That API is for T-Mobile Netherlands, not for US.
Our detailed billing options for customers can be found online at my.t-mobile.com or through our T-Mobile app assuming you are on an eligible rate plan! https://support.t-mobile.com/docs/DOC-2504
Thanks for responding. I know those options already. what I'm looking for is a REST or some sort of API that you guys may provide to developers so I can query my billing info.
can you please ask your dev team ?!
We do not have a public API (it's actually pretty closely guarded even between internal teams for safety purposes) that would render you billing info due to security protocol.
Please let me know if you have any other questions!