WhatsApp behaving abnormally. Situation is serious

For two days, I m receiving Whatsapp audio calls from the same number. The number from which I m receiving the call was not calling me because he was on a flight traveling from India to Australia. I have received more than 400 calls from the same no. The moment I switch on my internet connection, I start getting these calls. Even while typing this message, I have received numerous calls. Neither have I m able to send or receive any messages since that night. I have already switched off and on my phone numerous times. Also, I have uninstalled and reinstalled my Whatsapp. My daily activity is getting hampered. Any help will be appreciated.