Online brand threatening to file a lawsuit against me. What to do

Ordered 3 pieces from a brand during sale on 14 Sept after reaching out to them via Instagram DM & gave them my measurements,was suggested size M by owner.confirmed size as sale had a no return/exchange policy.I ordered size M.Recevd order on 20th Sept,tried it 1st time on 31st Oct & they didn't fit.The pants were'nt my size so reached to them on 31st Oct with this issue where they agreed my ideal size is top M & bottom L.Was told not to worry, they will exchange 2 sets.I shared a photo of me in M size, then I was told XL would be ideal.Exchange in XL was promised on 5th Nov,following up with them via Insta DM but keep getting response like fabric is out of stock,will ask owner to call you,telling me on 8th Dec they will get back to me at 11am but didnt.I informed them I will be raising a consumer grievance & they called this bullying. Raised the grievance & owner messaged me on Insta saying they will file a lawsuit against me for harassing,cheating & threatening for financial gain