I have a hard time imagining Tim League fabricating this. It would seem out of character from the way he runs the rest of his business, at least.
But the most important thing is, the enforcement of the rules behind the scenario in the voicemail is unflinchingly real. And given how much that clashes with the over-entitled brat crowd, I have little doubt that there have been voicemails like this left on the Alamo machines.
http://www.youtube.com/watch?v=1L3eeC2lJZs
tl;dwatch:
customer: I was texting and you kicked me out; whine whine whine
alamo: gtfo and don't come back