The majority of complaints filed against cab drivers with the commission that regulates them reference — drum roll please — credit card readers.

WJLA obtained the more than 650 complaints filed with the agency during the first six months of this year.

Two-hundred-seventy-one of the complaints obtained mentioned problems with credit cards, with some claiming drivers refused to accept them and demanded cash instead. In others, customers claim malfunctions with the machine prevented them from using their credit cards.

Other common complaints include rude drivers (147), refusal to haul (130) and overcharging (120).

A random test conducted by the D.C. Taxicab Commission in December found 94 percent of cabs had working credit card systems. Cab drivers were required to have credit card readers installed in October 2013.