After receiving jac's number, the first time you call him the next morning he explains he was up late, asks how the player is doing, and then the phone reverts back to the main menu and his dialogue quits. The game doesn't crash and I tried calling him again, but it quits every time.
For anyone who has this issue, I found a way to work around it. Jax can't be the only person who you meet. I.E. After reading Lennian's message I thought I missed something so I went back and tried again, This time thought I talked to more than just jax, in my case Dustin (I think that was his name, lol. The lion) and instead of Jax's phone call ending it went forward. Tl;dr socialize with more than your favorite lizard.
just if someone has the same problem, try getting the others numbers before getting jax's. I got thru by getting dustins and seth's.