Too late for OP, but for future reference:

Here is a list of licensed taxis in San Francisco. https://www.sfmta.com/getting-around/taxi/directory

Flywheel and Yellow Cab are by far the largest and probably account for most of the market. You can't go wrong by calling either one, or using their apps (link at the top of the page). Some of the others I've never heard of, they may be one-man companies.

From Marina district, I would take a cab to downtown and then take BART straight into the airport. This will be cheaper and probably about the same amount of time depending on traffic.