Howie, previously an associate director, will work alongside Dominic Williams, the head of press at Carat, and will report to Steve Platt, Aegis Media's head of media.
Steve Hobbs, Carat's head of media, will work alongside Howie and Williams and will run Carat's 115-strong planning and buying team.
The changes follow the departure of Mark Jarvis, the previous head of trading at Carat, earlier this year. Neil Jones, the managing director of Carat, had considered replacing Jarvis with external candidates but has opted instead for the internal restructuring.
Jones said: "This senior level appointment will take Carat's trading team to the next level. Azon has an impressive track record, especially in the last six months while he has been working in TV trading with Steve Platt.
"Azon proved he had the strongest credentials for the job against all internal and external candidates considered, and is set to be a valuable addition to Carat's senior team."
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