Trade Classifieds = Trash?

We made a deal to buy a tip trailer from Trade Classifieds in George, Western Cape.

As agreed upon in multiple emails, we were to pay a deposit, after which the trailer would be delivered, and before the trailer is offloaded at our premises, the rest of the money was to be paid to Trade Classifieds.

However, they never sent the trailer, and after multiple tries at contacting them, they informed us that the trailer was sold to someone else.They agreed to pay back our deposit.

This was 3 months ago and they just keep promising to pay back the deposit, but now they don't even answer the phone anymore.