Unethical, Unreliable, Dishonest Company

We paid in full for 2 Airconditioners to be installed in our offices, it took them 3 days to do the installation, 1 of the Aircons don't work as it does not cool the office, they say we now need a bigger Aircon even though they sent out somebody from their offices to give us a quote before we gave the go ahead. We are now sitting with a aircon that doesn't cool the office, we are using a fan and we have paid them in full. They continuously give us the run around, I am basically begging and threatening them to sort out the aircon, this has been going on for 5 days so far with empty promises from their side. When I send them emails, they hardly ever respond, I am the one sending emails to them and phoning them. I would recommend that you don't deal with this Company otherwise you are going to be a very dissatisfied customer. If they are behaving like this with the installation, how will they behave when it comes to servicing the aircons.