I had it free for three months and then increased the price, but KDP is still giving it away for free. Please check Pretty Little Girl by Don Canaan. It has been 2 weeks since I changed the price
Well, it can't be exclusive to Amazon if you had it for free that long. Which means one of 2 things: Either you didn't get the price changed at all of the other retailers, or the price change hasn't gone through at all the other retailers yet.
Amazon's price-matching. The 0 price match won't stop until all other retailers are showing the same price.