Standing in line to pay for groceries in an unfamiliar grocery store, you realize they have discount card savings programs. You don't have a card. And because you don't know when you'll be shopping here again, signing up to get a few cents off doesn't feel like it's worth the effort.

There's a quick solution for that. Remember that '80s classic from Tommy Tutone?

"Jenny, don't change your number." 867-5309.

I tried it recently while traveling in Maui. Not having a card for the island grocery chain, Foodland, I typed in the local area code followed by Jenny's unforgettable digits.

808-867-5309. Cha-ching. Discount registered.

It also worked at a Safeway gas station in San Jose, CA (408-867-5309). But the Safeway gas station in Santa Cruz, CA, rejected my attempts (831-867-5309).

So, why does this phone number work so much of the time?

When signing up for discount club cards, some customers don't want to use their own number. The first fake one to come to many minds is Jenny's, making it a hit in most area codes because someone has already put it into the system.

So, if you are traveling and lack a discount club card, try punching in the local area code followed by 867-5309, and reap the benefits of an iconic number.