Help! My DM is asking to work in QA from Automation

Hi Friends, I have been asked to move from python Automation to Manual QA job I have 3yoe python Automation in TCs I am not interested but after multiple pressured discussions from DM saying business loses this that I need to take up this opportunity.

After all the fighting he said I need to work on this QA role with Customer for 3 to 4 months and he will release my promotion which was on hold for 2yrs.

If I am not released from the QA role then my career will go backwards and if I dont take this role my then I all know the policy politics.

Suggestions needed.