Bests & Worsts Reviews from Amazon

I'm really disappointed with this order. I've ordered many bottles of this serum and it's always been perfect. Sealed up good, serum is clear (like it's supposed to be), doesn't smell funny. I got my new bottle in the mail today and opened up the box and my serum is yellow. This means it's already oxidized and worthless. i don't know how it's already ruined when I literally just took the plastic seal off the top and opened it. I need to contact them and get a refund or exchange but I'm not sure how. UPDATE::: I contacted them and told them my issue and they emailed me back a couple hours later saying there sending me a new bottle. The picture I inserted is of my old bottle from a couple months ago (on the left) next to the brand new I literally opened a few hours ago(on the right). You can definitely see how the older one is still clear and the BRAND NEW one is already oxidized and has a orange color. It should not look like that. They were very helpful though when I contacted them. I just hope the new bottle isn't going to be oxidized. I will keep you posted.