I don’t think Blizzard has directly handled the store for long time now so I doubt they can help you much. I think Fanatical handles them nowadays.
EU/UK store at https://www3.blizzardgearstore.com/customer-help-desk seems to have more contact options besides the email, assuming you ordered from the UK/EU store.
If you can’t contact them then probably best bet is to contact your credit card company and request refund that way if the Fanatics Customer Support is not responding.