Playing the linked .wav file, we hear DTMF tones followed by modem/fax noise. The DTMF tones decode to 17073365658; calling it, we hear more modem/fax moise. Okay, so maybe we're supposed to connect to it (BBS?); we grab a laptop with a modem, and use a landline and PuTTY to dial the number (because HyperTerminal is gone in Windows Vista and 7).
"NO CARRIER"; maybe it's not a modem. Let's go look for some fax decoding software.... (Hours later....) Damn, all I'm finding is commercial bullshit! Oh, wait, here's SpanDSP, an open-source soft fax library with some test programs.... (Hours later....) Damn, none of them can get any output from the .wav! Alright, this has to be easier than this; what about that modem?
Fire up Windows Fax and Scan, reconnect the laptop to a landline, dial that from another landline, and play the .wav file from an iPhone into the handset.
Holy shit; that actually worked?! The key is: BlastFromThePast^_^