supply 12000btu but charge for 18000btu

I would like to caution everybody from purchasing aircons from RefTech air conditioning due to what happened to me. I contacted Jonathan James early Jan 2016 for a 18000btu inverter air conditioner in my house. He requested 80% deposit. This is supposed to be a 2 day job AT MOST. However, three weeks later I still had no aircon because he said there is no stock. Then when he came to install the aircon, he installed a 12000btu and pulled off the stickers that shows the specs of the aircon. I asked him if its the right size as it looked a bit small and he said that the inverter aircons nowadays are much smaller. When he left I was suspicious and phoned the supplier who asked me to measure the dimensions and confirmed that it is a 12000btu. When I phoned him, he first argued that it is a 1800btu and then I said that the supplier confirmed that it is a 12000btu. He then said there must have been a mix up, but supplier said it's not possible as the box clearly states 12000btu and so does the stickers (which he torn off). At the end of the day he replaced it with a 18000btu. After all this (4 weeks), he sends me a message \payment?\" shortly after for the remaining 20%. Not professional "