I'd like to purchase the LG G5 through the online promo for $0. My tab is clear. I need to upgrade my plan to receive the promo. Should I upgrade my plan in self serve first then order the phone? I added both the new phone and the plan to my cart and purchased however it did not recognize that I have an existing account and has billed me for a new SIM card which I do not need. The purchase was also not recognized within my account and my plan has not changed. I am confused as to the steps I should have taken and how to move forward.