HELP!!! Need activation code or to Delete my Number!!!

I added my cell number so i could use twitter with my phone. they sent me a text with a verification code to my phone but I didn't get a chance to reply and activate before my inbox filled up and deleted it. Now when I try to add my phone number again, it says "this number is already in use". How can I get a new verification code, or get my number deleted so I can start over?