The operator set out the change, which took effect on Thursday (1 May), in an email to agents.
The new number is 0333 006 8799. Agents should select option one for pre-travel services, option two for new sales enquiries and option three for group enquiries featuring 10 or more passengers.
Jet2 is also directing a wider range of enquiries, including smaller amendments and queries, to the Manage My Booking section of its trade website.
It follows a concerted effort in recent months to roll out a wider range of self-service options for agents, and the reintroduction of a live chat function.
Agents were last month set a 9 April deadline to address smaller queries online rather than go through the contact centre.
These included online check-in and issuing boarding passes, adding essentials, amending names and dates of birth, and upgrading room and board basis, among others.
Speaking at last year’s Jet2holidays conference, director of digital James Malyon said the airline and operator was investing in tools to help agents be more efficient and empower them to make these amendments and changes in their own time.
Malyon added Jet2 was planning to have full self-service capability for amendments by the end of the year, and revealed the brand was working towards a "full rebuild" of its trade website.