The transition left some drivers unable to pay at meters on the first morning of the change. No in-app notice directed PayByPhone users to the replacement service, and kiosks did not display instructions pointing to ParkMobile, according to accounts from drivers who encountered the switch that day.

ParkMobile charges per-transaction convenience fees. The app also offers a monthly subscription plan that waives those fees — an added cost that did not exist under the city's previous payment arrangement. PayByPhone also assessed convenience fees, which some drivers say they did not realize they had been paying.

The shift raises a procedural question that the agency has not addressed publicly: what competitive process, if any, governed the selection of ParkMobile as the sole mobile payment vendor, and whether the convenience fee structure was reviewed as part of that agreement.

SFMTA did not respond to a request for comment on the timeline, the vendor selection process, or whether it plans to publish notice of the change.

Drivers and transit advocates have separately raised the question of whether per-transaction convenience fees on a government-mandated payment system are permissible under state law. That question has not been tested publicly before a relevant body.

Watch for: Whether SFMTA posts a formal public notice about the vendor change, any Board of Supervisors inquiry into the contract terms, and whether the convenience fee structure draws a legal challenge or a complaint to the City Controller's office.