Oakland: QuikPark Airport Express

Twice, when coming into the airport after midnight, I've called Quik Park's phone number with no answer over an extended period of time (20-30 mins). The first time the shuttle bus appeared after 20 mins even though I was unable to reach them. However, last night I had to hire a cab to drive me to the parking lot after I waited over 30 mins (1:30am to +2am) in the cold. When I arrived by cab, there was no one at the cashier's booth and the driver was sitting in his shuttle. When I was ready to leave, the shuttle driver ran over to complete the transaction and explained that the cashier wasn't around so no one was there to answer the phone. From where his shuttle was parked (with him sitting in it), he had a clear view of the cashier's booth and was obviously aware that no one was able to answer the phone.