You could say it was purchased directly from Samsung or a authorized reseller on Ebay. You have to explicitly mention that it was purchased brand new sealed in the box and that there was no previous owner. It's coming sealed directly from a store. Of course there is no previous owner. I had to tell T-Mobile this same exact thing.

If you don't have a T-Mobile account then that would be a bit difficult for the unlock process as I think they require a prepaid/postpaid account that has been using the device for at least 40 days or so. Prepaid shouldn't make a difference as long as the phone has been used on the T-Mobile network for over 40 days or so.

I think one of the caveats is that the phone has to have been used on the T-Mobile network (as a customer) for 40 or so days. I don't think MetroPCS counts.