Bill, it's not like she gave you her real phone number, dude. Best case scenario, you can call that number to order a pizza. Unfortunately, it's hard to pick which scenario would be the worst case.
Scenario 1: The phone rings within a top secret government installation, triggering a massive military response as every single governmental agency with an acronym receives orders to terminate you with extreme prejudice. Oh, and there's no more pie. I'm not sure what that has to do with it, but it kinda amps up the horror just a bit.
Scenario 2: The phone is answered by an evil genius who is in the process of breaking out of the Des Moines Institute for the Criminally Insane. This genius traces your call and sends his minions to whisk you away to an underground lair where you'll be kept in a cage and have a perfect replica of Salvador Dali's
Persistence of Memory carved into your back with a vegetable peeler while listening to
Enter Sandman played on an accordion 24 hours a day.
Scenario 3: The phone is picked up by Bapu while he's wearing his Wonder Woman costume.
Scenario 4: The ringing phone startles a sleepy trader on Wall Street resulting in an unfortunate trade, accidentally devaluing becan and thereby plunging the entire world into an irreversible monetary collapse. In the ensuing apocalypse, whole continents are rendered uninhabitable, nations are wiped out, and the few survivors are forced into a bleak hopeless struggle for survival. Oh, and Justin Bieber is okay.
Scenario 5: The ringtone of the phone at the other end of the call sounds, unfortunately, exactly like a declaration of war to Hbthrk*!#$lp, who is the General of a massive alien invasion force determined to claim Earth as their new home. In addition, they brought their own vuvuzelas.