The phrase "already been serving" is correct and usable in written English.
It can be used to indicate that someone or something has been providing a service for a period of time prior to the present moment.
Example: "The restaurant has already been serving customers for over a decade, establishing a loyal clientele."
Alternatives: "has been providing" or "has been catering".
Mr. Ngcobo had already been serving on South Africa's highest court, the Constitutional Court.
The new American ambassador, David Brown, has already been serving as senior adviser to CAR since August last year.
Mr. Shirakawa had already been serving as the bank's acting chief since winning approval from Parliament last month to become one of its two deputy governors.
I'm already a congressman, so I was asked by my colleagues to take a responsibility within Congress that I've already been serving in from the one that I had.
DS Johannesburg – Gil streetHeron When street poet musician Gil Scott-Heron wrote this song in 1974, most of America (and the rest of the world) had no idea who Nelson Mandela was, let alone that he had already been serving 12 years of a life sentence by then.
Sam S. F. Caligiuri, the president of the Board of Aldermen who has been serving as acting mayor, said that Mr. Dakers had already been serving in the role and that the unanimous decision by the board formalized the arrangement, giving Mr. Dakers added authority over fiscal policy.
Tax notices have already been served to these companies, the article said.
As the six-month bans have already been served, they are now eligible to compete.
Some good has already been served by Barkley's N.C.A.A. problems.
However, Aamer's burgeoning legend has already been served well enough here over the last few days.
Evidence relating to these further counts has already been served to the court and the defence, the CPS said.
