What is the procedure for withdrawing Voluntary Retirement notice in case of Group A officer?

I have submitted voluntary retirement notice after completion of 33 years of qualified service for 3 months with effect from 31 December 2020. Now I want to withdraw the vol. Retirement notice . What is the procedure in cae of A class officer.

As per DoPT O.M. No.25013/7/77-Estt.(A) dt.26.8.1977:

A notice of voluntary retirement may be withdrawn subsequently only with the approval of the appointing authority provided the request for such withdrawal is made before the expiry of the notice.

From your question, it is not clear whether your request for VR has been accepted by the appointing authority. If not, that can be withdrawn.