AT&T spends a lot of time and money polishing its brand and its reputation. It was ranked 49th in Fortune's Most Admired List, and number one in the global telecommunications category earlier this year.

So Chief Executive Randall Stephenson must be concerned about the negative publicity surrounding the company's $600,000 payment to Michael Cohen, President Donald Trump's personal lawyer.

Stephenson, who is waiting for a Federal Judge to rule that AT&T can proceed with its acquisition of content giant Time Warner, must have hoped that parting ways with Robert Quinn, the company's Washington D.C. chief, last week would at least help the company get back on the right track.

But on Monday, a group of Senate Democrats dug in, sending a letter to AT&T looking for more details of on the who-knew-what-when.

At the time Cohen began as a consultant, AT&T was seeking approval of its $85.4 billion acquisition of Time Warner, which months later was met by a Justice Department lawsuit. President Trump has said he did not believe the merger is in the public interest and has been highly critical of CNN and its chief executive Jeff Zucker. In April, Trump sent a tweet suggesting Zucker's job was in jeopardy.

The letter to AT&T was signed by Sen. Elizabeth Warren, D-Mass., Sen. Richard Blumenthal, D-Conn., and Sen. Ron Wyden, D-Ore. The Senators want to know if there's a pay-to-play going on. Take a look at the intriguing question number eight. Read the letter here. 

Wyden also sent a letter asking Novartis, which also paid Cohen, for details of their relationship. 

AT&T said it was aware of the letter and will be issuing a response.