Incomplete order and company stopped responding to my emails to explain their deviation.

I made an order or two dresses with this company and paid for it. I’ve been communicating with them via email while my order was being processed. Yesterday I received my order having only one dress inside and the tracking system says 2/2 or my order has been delivered. I’ve sent them emails and now they do not get back to me. To make matters worse it’s the expensive dress that’s not part of the delivery . I want my second dress of refund on my the purchase.