Deleting old gamer tag and adding a new one to an account

[joejimenez54]

I need to delete my old gamer tag that accociated with my EA account for Xbox live because I no longer use it. I have a new one that I would like to add as a persona but when I click on add persona it takes me to another screen and asks me which one i would like to add. There are no choices to choose from. I've gonthorough to see if I can just disconnect my older GT from the account but there is no option for that ( at least one that i found). How do I go about this?