I bought a gig gave him negative reviews due to misunderstanding between us, but I want to change

I bought this gig more than 1 week back. http://www.fiverr.com/users/jordanraingam/orders/FO5420144CB8
Due to some misunderstanding I gave him negative ratings, but after serious talking and provided thorough instructions by the seller his service is working perfect. Please help me How can I change my negative reviews to Positive Reviews.
Thanks

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