Yes, that is exactly how it works
https://www.inmateaid.com/ask-the-inmate/so-i-want-to-get-the-discount-local-number-my-question-is-after-i-get-the-number-do-i-have-to-call-gtl-to-add-money-to-my-account-with-the-new-number.amp#answer
Accepted Answer Date Created: September 20,2014