scams and frauds

I don't know about this why this messages and call are coming but I was getting calls from unknown numbers and when i answer that call at that time no one is responding and I heard a ringing sound then that call has get cut by it self and after few seconds I am receiving a message that is otp message in that message a login otp is there i send email to Truecaller also because it is otp of Truecaller login please anyone can explain me what is happening this