Order Cancelled without explanation

I ordered items which were to be delivered in 2 days (lead time), 7 days went without delivery. I made several following-ups and only to receive an email from Amazon for cancelation of the order without any explanation. To me this is very unprofessional way of dealing with customers. I will never buy from them..... I'm still waiting for my refund and hoping to get it within 7 days as they promised.