You need to go into the left side of Facebook and tap or click on blocking. after Clicking on Blocking in the left-hand menu. you have to enter the name of the person to whom you want to block and tap on the block. Select the particular person you desire to block from the list that appears and click on Block> Block. Take Facebook Customer Service1-855-479-3999 for knowing more. https://www.mailsupportnumber.com/facebook-customer-service-contact-number.html