Seven state Democratic leaders demanded accountability from FDOT officials in Miami on Wednesday morning after a press conference on what they call "Tollgate," the state's oversight of the failed SunPass tolling system.

Rep. Kionne McGhee, D-Miami, who led the press conference, said they met with District 6 Secretary James Wolfe and spoke with FDOT Secretary Mike Dew's chief of staff, Shannan Schuessler.

"We now know that the FDOT has firsthand knowledge of residents being double-billed," McGhee said in an interview with the Times.

Wolfe said he couldn't speak to the double-billing because he doesn't see the SunPass accounts, but said Schuessler didn't actually say this.

In an email, interim FDOT communications director Ed Seifert said, "During the initial rollout of the new system, a few customers experienced double billing but the errors were caught very early in the process. SunPass staff worked with each customer, individually, to ensure that their accounts were accurate. SunPass continues to verify every account transaction for accuracy."

The Democrats want Gov. Rick Scott to suspend all SunPass toll collections until the system is fixed and to appoint an independent auditing committee to investigate FDOT's oversight of the SunPass system.

Other state representatives that were present at the news conference were Barbara Watson, D-Miami, Robert Asencio, D-Miami, Roy Hardemon, D-Miami, Anika Omphroy, D-Lauderdale Lakes, and Sens. Daphne Campbell and Annette Taddeo, D-Miami.

McGhee said FDOT officials asked the representatives to address their questions in writing and did not provide specific numbers about how many backlogged tolls still need to be processed.

Related coverage: Democrats want Florida to suspend all SunPass toll collections until the system is fixed

Taddeo spoke about her experience trying to set up a new SunPass account for the last two weeks. She said she's tried the customer service website, app and phone lines, but nothing worked.

"After my tweet, someone did call me back and left a voicemail," she said. "But I wonder how many regular people get that kind of call."

Taddeo said she doesn't expect much from FDOT because the agency chose Conduent despite its track record of tolling system problems in other states.

Related coverage: SunPass is a mess. Florida could have seen it coming.

"Where I represent, you cannot go anywhere without getting on the Turnpike, which means huge fees," she said in an interview with the Times. "I'm really concerned."

The SunPass customer service website, call line and app started malfunctioning in early June during a system update, and since then many SunPass users haven't seen accurate toll charges posted to their accounts.

FDOT's Seifert said Wednesday that "the total backlog of transactions including SunPass transactions are 170 million. SunPass is working diligently to clear the backlog of toll transactions."