Fill out a proper scam accusation.
These Starbucks cards are stolen/cracked, I assume? If that's the case then you both ought to lose your money. Sorry, I don't have much sympathy for either end of these deals.
Looking at his other posts, it appears to be the case.

I want u delete feedback on my profile. I change another giftcard for him. Anyway, i lose money, and get bad feedback.
Contact Vod directly about it he may change his feedback.
As I see it here, getting a red reputation is easy, but once the problem is solved, getting the red removed is harder than you think, and longer too.