Airtel — closed my 3g sim without my permission and convincing me to convert into 4g

Address:	176306
Website:	www.airtel.in

Earlier i was having 3g mobile, few days before i purchase a 4g mobile but using 3g sim which was working in good condition. Started getting msg from airtel that convert your sim, i denied. Today they shutdown my internet services. When i called to customer care they inform me that there are some network issues and will be resolved shortly. Then after 5 minutes they blocked my sim. When i contacted customer care they started persuading me to purchase 4g sim. I denied and ask them to unblock my sim.
Very surprised that airtel people are adopting such unethical ways to promote their 4g market.