I got a message saying my phone number and Apple ID are being used for iMessage and FaceTime on a new ipad

Do you own an iPad named Sharda's iPad?

Did you sign into iMessage, Facetime and iCloud with your Apple ID?

If so, its probably just renewing the service activation for them.

If you don't own an iPad, do you share an Apple ID with someone that does have an iPad?

Well if that's your name that's shown in the notification then it's highly unlikely that someone signed in on an unauthorized device. There could be a number of reasons that if your iPad was already signed in, it had to re-sign in again.