Your employer is Artech.
You must have submitted notice of resignation and must have obtained acknowledgment.
You have served the notice period.
Probably due to work exigencies IBM is asking Artech for your availability, and all this is verbally.
Your employer should communicate in writing to you whatever they wish.
You may express yourself to your reporting authorities and settle amicably.
otherwise you have resigned and you can demand your payouts,F&F,work experience certificate,PF accumulation report,form16,work experience certificate, releivng letter.
You may raise your claim under receipt from your employer.If you re not satisfied you may submit in writing to your appointing authority,MD,CEO,COO,Head-HR,Company secretary.If you are not provided relief you can raise greivance with the regional office of labour commissiner in your town.