Bought an iPhone off ebay, it is locked. Can apple flash it?

I bought a 5s off of ebay. 2 year warranty and it was unopened. When I tried activating I needed the original owners last 4 ssn and billing zip. I had brought the phone earlier to att And we switched sims but to no avail.

So eventually the guy gave me his ssn and zip but now I need the original sim which the guy at att threw away. Can Apple flash the phone to its original state? I already tried restoring to default settings.

Yes, but you had better hope it is not stolen.