Hi @Keyon12 do you remember using or linking your phone number to an Airbnb profile? That is why you're unable to verify your phone number. When you contact Airbnb support, clearly explain that you are receiving a message stating that your phone number is already in use and that you cannot verify it for your account.
Depending on their investigation, the Airbnb support team may provide specific instructions or steps to follow for you to use your phone number to this Airbnb account successfully. Hope this helps!