You know how you give the business card to Jim, and he phones Wilbur immediately? It's too bad we couldn't hear their conversation; however, that doesn't stop our imagination...
Wilbur: "Hello?" Jim: "I got your business card. Are you the one to call about 'taking care of problems?'" Wilbur: "That's me. What's your 'problem?'" Jim: "I'm the owner of Jim's Shack O' Crabs in the center of town. I've got some rats here that I don't want to have around." Wilbur: (He thinks Jim's speaking figuratively.) "You've called the right man. Can I meet you in person, and you can point them out to me when I get there?" ...and so forth.
I personally wonder why the conversation lasts so long (for the rest of the game, in fact!). I'd think that Wilbur would hang up rudely as soon as he realized exactly what Jim wanted.
And why the heck did Wilbur choose the number of that pay phone in front of the Boss's office for his business card? Sure, it'd be nearby, but it'd be pretty inconvenient if he was anywhere besides guarding the Boss's door.