Bring it with you just to be safe
and the amount of time since you got the phone
Not usually. Most cases its in the system. As long as you have a receipt you should be fine.
It all depends on the value of the exchange. If the phone you are getting is valued at more than the one you are turning in then yes they will need to run your card again. If the value is less they will simply refund the difference back to your card. I'd say bring it just in case
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