I''ve had some very helpful cabbies, i.e., helping me with my luggage and waiting (with the meter running) for me to run up to the office and get my mail. Flash cab is best.
As for the phone, it's hard to conduct business on a cellphone with someone rambling in a foreign language or listening to reggae music in the background. I've had clients ask me "Where the hell are you?" while I'm on the phone. Now I tell the cabbies to turn down the radio and be quiet when I have to make a call.
Steve