A former official at Brewster Ambulance Services has sued the company, accusing it of defrauding Medicare by charging for unnecessary ambulance rides to dialysis appointments.

In the lawsuit filed last week, Brendan Cameron says he was fired after raising concerns about billing Medicare for rides that weren't medically necessary. Cameron, a former revenue director for the company, is seeking $134,800, including $108,000 in lost wages and $25,000 in "other damages."

Mark Brewster, the company's president and CEO, said Wednesday that the allegations are "absolutely untrue."

"It's a disgruntled former employee and there will be a countersuit," he said.

Cameron said problems started in his first month as a full-time employee in October when he found $500,000 in overpayments dating to 2017 that required refunds, including refunds to Medicare and Medicaid, the complaint states.

Cameron said the company was facing financial pressure. In early November, one the company's owners, unnamed in the complaint, "made it known" that he put $4 million into the company to maintain its solvency, according to the complaint.

It's not clear who at the company the lawsuit is referring to. Filings with the secretary of state's office name Mark Brewster as the president and treasurer of the company and George Brewster Sr. as the secretary. According to the company's website, Mark Brewster is the president and CEO while George Brewster is a "senior adviser."

During the second week of November, Cameron said, he started reviewing dialysis claims at the request of a subordinate who found "numerous" patients did not have paperwork indicating that they had a medical need for ambulance transport as required by Medicare.

Many dialysis patients did not meet the Medicare standard for ambulance transport because they could walk or sit up on their own, as documented in the narratives of the emergency medical technicians, but their services were still billed to Medicare, the complaint said.

"Mr. Cameron brought the dialysis claims issues, and other improper billing practices, to his boss, the owner/executive," the complaint stated. "The owner/executive disagreed with Mr. Cameron and strongly argued that the patients at issue required ambulance transport."

Cameron said he told the "owner/executive" that, based on the narratives, Medicare should not have been billed and that intentionally billing at a higher level than medically necessary was fraudulent. Several patients were being taken to dialysis each week by ambulance, the complaint stated.

At some point, Cameron said he was instructed to stop reading patient narratives when reviewing claims so they could be processed faster, but Cameron pushed back because billing without reading the narrative would be fraudulent because it would be "impossible" to determine whether a trip was medically necessary, according to the complaint.

On Nov. 27, Cameron was told to lay off nine of his staff members to reduce costs. On Dec. 3, the "owner/executive" told Cameron's department that no refunds were to be issued to Medicare or to any other payers unless he approved them, according to the complaint.

After pushback from the billing department, the department was broken into two "teams" and Cameron was placed in charge of the team dealing with "work denials" and follow-up on unpaid claims, which was a demotion from the job for which he had been hired and "kept him away" from Medicare compliance, according to the complaint.

In December, the complaint states, the chief financial officer gave Cameron permission to work remotely. When he returned to the office in January, Cameron said the "owner/executive" was upset he had not been in the office, accused him of causing dissent and said he had not "done anything for the department except 'write off money.'" Then he fired Cameron, according to the complaint.

Cameron's attorney, Serena Madar, of Quincy, declined to comment Wednesday.

Brewster is based in Weymouth and provides 911 emergency services for Quincy, Braintree, Plymouth and Brockton.