This. I'm all of punishing the hell out of cabbies that cheat (e.g., fare refusals or the out-of-city overcharged fares that were discovered via GPS data), but the failure to get into the cab ruins the whole case.

Get in the cab. State your business. Snap a photo of the driver's license if you are asked to leave and report him/her to 311. Blog to your heart's content on behalf of your company's alternative service.