Hi @erberw!
Welcome to our Community Forums! Adding a new line to your account can definitely be an exciting experience. I will be glad to provide some additional details.
Upon adding a line to your existing account, the process requires a credit check which will determine if a deposit is required. The check will also check for any delinquency on the account. If the account is active and in good standing, you will then be able to complete your purchase.
I hope this answers your inquiry. Please have an excellent weekend!
Shenoah, AT&T Community Specialist