Payment fixation on demotion - fixed me in the starting scale of the Senior Manager

Dear Sir, I have recently(on 3rd March 2020) been demoted from AGM to Senior Manager on some flimsy grounds by the management. Whilst doing so, they have fixed me in the starting scale of the Senior Manager which is a basic of Rs.25500/- whereas when I was promoted in Oct 2019, I was drawing a basic of Rs.39000/-. Want to know whether this is correct as per the HR rules/regulations. Also, keeping in view, that all my terminal benefits like gratuity, incentives, HRA and other allowances which are dependant on the basic pay, I am put to extreme hardship to deal this situation. Can anyone please guide/advice me for further course of action. Thanks, Regards.

Dear friend,
Since you were promoted in October,2019 only as AGM from the post of Senior Manager, my opinion is that your pay should have been fixed on the last drawn basic pay at the scale of S.M on your demotion as S.M.

Even if you were on Probation-on-Promotion and your Employer took an Arbitrary Decision to "Demote you to your Pre-Promoted Position, Reducing your Basic Salary you were drawing at the Time of such Promotion Ought to be Restored to remain in alignment with the Duties, Responsibilities and Role alloted to you in your pre-promoted Position failing which the Arbitrary Act of Demotion tantamounts to Unlawful, Unethical, and Condemnable Act in a Civilized Society.
Demotion in any Case is an Outcome of Disciplinary Action for an Act of Misconduct/Unacceptable Act. Seek Remedy
Harsh K Sharan, Kritarth Team,
10.5.20

Yes, fixing the pay at the starting stage is wrong unless, of course, the Order imposing punishment mandates so.

I go along with Umankathan that your salary should have been put at the last salary drawn at the Senior Manager before the promotion.

I mean the last salary point drawn at the position of senior manager before you got promoted to AGM.

I agree with the members in the discussion here,
The salary should have been reduced to what you were drawing in Oct'19 because after all, it is because you had been performing well, that you got promoted from that level.
So reducing your salary below this level would be unfair and against the management's assessment of your performance when you were promoted in Oct'19.