I have a very old phone but I like the plan I'm on. I want to get the HTC phone now but when I add the phone online, it is telling me to choose from their list of current plans. My old plan is way better than them.
Can I get a new phone without having to lose my old plan?
Since you're buying online it should only ask you to pick a plan if the site thinks you're a new customer.
After adding the phone to your cart; go to check out on the right hand side of the phone. Then you can click "Check out" and the site will ask you if you're a new or existing customer. click existing customer, inputs the login info for your Self Serve account and then you can proceed to order.