Factual error: When the cell phones are switched, Melanie's mom asks Jack what his cell is and he says Pennsylvania-something. The old-fashioned system, over a half-century old of having a two-letter denomination for the area or town, such as PA for the area around Penn Station, or LI, for Long Island, is followed by five digits, but Jack gave four digits, so it wouldn't have been an actual phone number.
Suggested correction: Pennsylvania 3317 is the area code. First three numbers are for that area in New York, Then 3317. 10 numbers.
I think it's the New York area code, which for early cell phones in 1996 was most likely 917, then, the area code for all of Pennsylvania in 1996 was 814. I think Jack is saying his number is 814-3317. He wouldn't need to specify the area code since at the time you only included it when dialling out of your own region, or if dialling a mobile number - and the phone Rita's calling would surely have had the same 917 area code as Melanie's, since 917 phones like the star-taks were not yet common.