Airtel — resume sms service on airtel sim

I have upgraded my old airtel sim to 4g i have got the sms that for security purpose sms services will be blocked for 24 hours

Important update: sim change request has been initiated for airtel mobile 77*. Sms service will be resumed after 24 hrs. If not requested for sim change, sms nsim to 51619 immediately.
Congratulations! Your new sim no has been activated for your airtel mobile.

Now it has been 5 days still sms service is not resumed on my number i request you to please resume it as soon as possible