Hey beiu! Early congratulations on your new phone! I'm glad you're asking before heading out. In order to complete an upgrade, you'll need a credit or debit card at the store to cover your up front charges. You can use a prepaid credit or debit card to cover those costs, but you'll want to add an extra dollar or two so that you can be sure there's enough to cover the authentication charge and the actual up front amount. The way that those prepaid cards work, what we've seen is that they don't release the dollar hold that we place to verify a card as quickly as your bank account or actual charge line would, which can result in your full charge being declined once it's time to complete that up front payment. Let me know if you have any other questions about upgrading!
Hey hey! Were you able to get your upgrade started? Which phone did you choose??