Lip plumper refund?

I bought some lip serum for 34 pounds from a Christian Dior counter at the House of Fraser that's supposed to plump the lips. I still have the receipt. I've been using it five times a day for two weeks but my lips look exactly the same. If I went back for a refund, would she just tell me where to go? I know that the istants make money on the sales on those counters.