Ok so you have looked at the other clans site and they have exactly the same clan tag ....
prior or to ghost they gave everyone a chance to reserve their clan name and if they didn't reserve it they risked losing it regardless of when they started their clan ,,, that's why I reserved mine right away
prior or to that if I remember correctly whoever reached gold first got to keep their clan tag
beachhead studio twitter since they are the ones that created the app would be the place to go but you might get a quicker response at treybeachhead twitter who also works there.