Airtel — unethical and rude behaviour

There was a call from Airtel Customer care no. [protected] for changing my existing mobile network to Airtel, I declined the offer and disconnected the call. After few minutes I got a WhatsApp message from the same number using abusive and rude language which was not at all acceptable .This is a very serious issue and I request urgent and strict action against the person who has harassed me using abusive language. I Have proof as Whatsapp screenshot which I can share further.