How You Can Remove yourself from the blacklist?
The first step is to go to your Whats app with that no. that is blocked. And take the Chat back first. If you don't know how to then you can do it by going to the setting, clicking on the three dots on the bottom right corner and then Chat and Chat backup.
And now go back and click on the Account on the last delete my account. And Now enter your no. and click on delete my account. now what had happened is all the info about your what's app account has been removed from the database of What's app. Now Install Whatsapp beta and create an account with the same no. and you will find it unblocked by the users.
Updated - Now this process is not working because of the Whatsapp update. This process now worked in updated Whatsapp apps. If you will try to unblock yourself in new Whatsapp then you probably lose your Whatsapp account and chats. If you do this you also will lose you're Whatsapp chat backup. So I will suggest you to not do this process if you have updated Whatsapp of march 2020.