Car Service from SFO to Fisherman's Wharf

[DisneyFans4]

Can anyone recommend a car service to bring us from the airport to the Sheraton Fisherman's Wharf? I called the hotel and they don't have a car service but said there is a shuttle bus but it costs about $20 per person and there are 4 of us. I think a cab would probably end up the same cost as a town car but I don't know who to call.

Thanks so much!!