Yeah, Prostitution is still mostly illegal, but using company resources to do so, is probably pretty fireable.
The way the AD of the university described, the only call that showed up in Coach Nutt's FOIA requested logs, was a 30 second call. So they took it upon themselves to look further into Freeze's logs (the ones that maybe Nutt didn't FOIA for) and "found a seriously troubling pattern" but didn't get into exactly what that means. Just enough that they told Freeze to resign or be fired with cause, cause they "No Buyout/No Settlement" him, a rare thing in today's Football coaching.