I've been digging around on the AMD Store pages trying to find any actual contact information, but, as you said, there's no way to actually contact anyone about an order. You can look up your order status, but AFAIK, you can't actually tell them about a problem with the order.
Looking back at the email receipt for an old order I made on the store, there's the following at the bottom:
"DR globalTech Inc. is the authorized reseller and merchant of the products and services offered within this store."
The link it points to is:
https://store.digitalriver.com/store/defaults/en_US/DisplayDRAboutDigitalRiverPage/eCommerceProvider...
And, from there, I used the Terms of Sale link at the top of that page to get to:
https://store.digitalriver.com/DRHM/store?Action=DisplayDRTermsAndConditionsPage&SiteID=defaults&Loc...
And, on that page, I see:
Identity of Operator
Time has passed since I placed that order and you're from somewhere else than me. So, all of that might be different in your case. But, at least it gives you a possible process to try to find someone to actually contact. Assuming DR also shipped your stuff, that
onlinestore.en.cs@digitalriver.com is probably a decent place to start if you can't find anything else.
Hard to believe that a major corporation would have a store where they don't care about anything.
EDIT: And, I'm not certain how valid the above will be since this forum's software just complained about something in it and changed something random.