Phone Number And iMessage

When I try to add my phone number to iMessage I get an error message that the number is being used with another account. When I first got the phone I signed in just fine then I had to erase the phone. After it was erased I tried to log back in with the same iCloud information but it would not let me add my number. I have tried going in and making sure the number isn’t the only trusted number, removing it from trusted numbers entirely, making sure it doesn’t show in personal information when I go to the iCloud website via computer. Nothing is working.