Non-existent customer service

I returned an item because it was not the same as depicted in the catalogue. I have now been trying for more than a month to speak to someone about a refund. I've used their return system on the website, and received a ticket number, but no further communication. I've emailed repeatedly, and had a "how can I help" from two different people; however, not one has responded further to my query. I've phoned a number of times, and only got the response that the mailbox is full, and cannot receive more messages. My next move will be to arrive on their doorstep.