I contacted them through the website for my missing TFA and through ZavviCS on Twitter for my 2 missing Solo copies. Both have taken several days to get a response. I also contacted them because my replacement ESB came looking like someone had used it for a drumming session but they haven't responded to that one in maybe 5 days now. I did just get this in a generic e-mail yesterday: "We’re sorry for our longer than usual response time, our teams are working hard to support your query."
I can only imagine that they are getting bombarded with inquiries from people about all the missing Star Wars steelbooks right now and they are probably behind on all of them, especially if people aren't just accepting the refunds without ongoing complaints.
I get a laugh that even though they don't offer any tracking at all and must certainly know by now that all the missing Solos are not due to postal error or thievery (I don't know if I've ever written the word thievery before, so thanks Zavvi), they still ask the same three questions: Whats your address? Did a member in your household sign for it? Did a neighbor sign for it?
I always tell them that I live with my cat but he assures me that he doesn't have it.