There are 4 other cab companies in Toontown.
A cabbie can refuse any fare they want to refuse. They are not obligate to take on the fare just because the fare wants them to.
I'm not entirely certain your laws work like ours do, but down here it's illegal to refuse a person for disability accommodation, just as it would be illegal to refuse a person because of her race. The cabbie and the cab company have a right to refuse a fare, but they may not refuse a fare for some reasons, such as race, sex, national origin, religion, disability, etc.