If it's one of the positive feedbacks then you cannot change those .
If it's the neutral you left, this was a purchase fom a Chinese seller. Please do not change the feedback if they are promising any refunds, or sending out a new item, this is a common ploy and they'll never fulfill that promise.
If they are promising something, ask them to do this first, then you'll ask them to send a feedback revision to complete, but not before.
