Select Paving & Interlocking

We called a company called Select Paving & Interlocking and an Irish man named Jim came to our house to give us a quote.
When we called later to book the job another man called Andrew answered the phone and said Jim was on vacation and he was in charge.
Andrew, also an Irish young man around 35 years old, came to our house with two other men and worked for three days cleaning the backyard. On the third day he asked for half of the money $6,500 to buy the stones and pay the bin for disposal. After he got the money, he didn't show up to work anymore. He completely disappeared with our money. He doesn't answer the phone or reply to our messages.
The address of this company is a residential building in Mississauga at 25 Trailwood Dr. They did not provide the unit number on their website. Their phone number is 365-778-6159 and 905-537-8527
It has been more than three weeks since they disappeared.
It is clear they won't come back and have no intentions of returning our money. We even did a contract and checked a reference prior to hiring them.

We reported this to the police but we would like to warn the next potential victims.