Take my money then ignore me.

Paid for and placed an order on 4th June that was acknowledged by them that same day. Queried progress of order via email on 15th June. I received an automated reply saying that they were very busy and that someone would respond within a day or two.

I have heard nothing since then. I have sent several emails, tried their online chat (no-one ever answered) and made several unanswered telephone calls to their office number ***.

I want what I have paid for. What must I do now?