Do you often indulge in group chats with several unknown people to whom you don't wanna reveal your phone number? Do not worry. You can do that. Here's how:
If you are already using WhatsApp, uninstall it from your device completely. You can keep the SD card files i.e. the images if you want. Download and install it again.
Now when you open WhatsApp it'll ask you to verify your phone number. It automatically sends a verification message to its server. But if this happens your number gets registered with them. So block your message service. You can simply put your phone on flight mode so that all network connections are disabled. You can alternatively change the message center number. Remember the old one of course.
It'll ask you to choose an alternate method to verify. Choose 'Verify through SMS' and give your email address. Click on 'Send' and without waiting even for a second click on 'Cancel'. This terminates the authorization process.
Now you have to spoof that message. You can try this for Android and Fake-a-Message for iOS.
Go to your Outbox -> Copy the message details to spoofer app -> Send it to spoofed verification.
Use the following details.
From: +(Country code)(mobile number)
Message: Your email address
A message will be sent through that spoofed number. You can use this number to connect with your friends.
I don't know if you should be trying this or not. I don't find it useful anyway. It's always a good idea to use your real phone number.