I made a tt capsule and I don't like the interior so I made a copper tardis and I was gonna place it down and think nothing of it, but then a guy in chat said you will get banned if you have more then 1 tardis, so what do I do? 

You can’t really delete a tardis. It will always be somewhere in the server files if you check the crafting recipes which you can see with the JEI items mod you can try make your first tardis with the tt capsule (Only if you didn’t placed a tardis down yet)

 Well is there  a way to change the interior with a chameleon circuit or something? 

 you can only change the exterior with a chameleon circuit. However if you wanted to change interior you could build it yourself.