We understand your predicament. Unless you are able to convince someone at the institution that is answering the phone to relay the number to him, you are going to have to spend the $0.49 and mail it to him.
https://www.inmateaid.com/ask-the-inmate/my-sons-father-is-locked-up-and-he-gets-out-soon-he-doesnt-have-my#answer
Accepted Answer Date Created: September 03,2016