Hi. I want to upgrade to a Captivate this weekend and I'm a authorized account user on my mom's AT&T account. The phone is cheaper at Walmart, but my sister told me that the sales person there said that they can only upgrade her line if the primary account holder is present, even though she is also an authorized user. We're both in college and it would be inconvenient to drive home. Is the AT&T store my only option to do the upgrade without my mom present?