act for/on behalf of sb/sth
phrasal verb with act verb [ I ] uk/ækt/ us
LAW
to represent a person, company, etc. in a court of law:
There are few exceptions to the rule that a solicitor may not act for both seller and buyer.
to represent a person, company, etc. or deal with their business for them:
The Council of Mortgage Lenders claims to act for 98% of lenders.
She was authorized by the Commission to act on its behalf.