In Beadnell, the new times are 3pm to 4.30pm on Wednesdays and 1.30pm to 2pm on Fridays, still adjacent to the Village Store, Harbour Road.
The service at the White Swan Inn car park, Lowick, will be 9am to 10.30am Monday and Wednesday; 11am to 12.30pm, Tuesday; 10.30am to noon, Thursday; and 10.30am to 11.30am, Friday.
In Rennington, in the car park next door to the Horseshoes pub, the service will change days from Monday to 2.15pm to 3.15pm on Friday.
The changes are the result of a new mobile service being introduced in Longhoughton.
With more than 11,500 branches, the Post Office network is the biggest retail network in the UK, with more branches than all the banks and building societies combined.