Worst services from Omninela medical

I ordered Fresubin (Order number #710790) from Omninela medical online, and the website indicated there was stock. After placing the order, i was informed much later after I first followed up with them that they had no stock. I asked for a refund. It has been so long and multiple emails to them and still do not have my refund. Now they don't even bother to respond to emails, yet they read it. How do I get my refund out of this supplier that keeps avoiding giving me my refund so I can go to another supplier to buy my sick dad his fresubin.