Yes, you do need to show a planned completion date for all your Sectional Completion Dates. See link below which discusses a similar question.
On your Client’s requests, your Sectional Completion Dates can only be moved forward by Acceleration (36.1) in NEC3. The rules for a sectional Completion Date are the same as the rules for a Completion Date. You as the Contractor can ‘refuse’ to do so.
If you have agreed to Accelerate and your Compensation Events are being assessed less than quoted your recourse is Adjudication unless you have an ADR procedure written into your contract.