Unreliable and unresponsive. Signed a contract and...

Unreliable and unresponsive. Signed a contract and paid a very large deposit at the beginning of July. The contract (which they provided) states that work will begin within 15 days and will be completed within 40 days. It is now October and work has not begun. They are unresponsive to emails and calls. The times when we have received responses, we have been told that "work will begin next week." Still, months later, nothing has been done. I'll be contacting the BBB.