Have Screen Will Travel

I contracted this company to replace some window screens at a revenue property I own. They quoted $140.00 plus GST. I gave them the go ahead to do the work and they made arrangements with the tenant to go on site and do the work. I was to pay them by credit card once the work was completed. I told them to call me after the work was done & I would pay them. When they had finished the job, Dan, the installer, called me on my cell phone for payment. Unfortunately, I was in meetings and missed the call. They called again and I was still unavailable. When my meeting was finished, I checked my voice mail and there was a message from a man named Dan telling me that "if I didn't call them back right away with a credit card number, he was going to leave with the screens". Unbelievable! I then called them as soon as I heard the message and they did not answer the phone. I then called the lady who rents the property to see if they were still there. She then told me that he had demanded payment from her because he could not reach me. He told her that he would remove the screens he had just installed and would take the screens with him. She said he was rude and intimidating and that her kids were very uncomfortable with what was happening. To save further escalation, she paid him and he left. The company had quoted $140.00 plus GST for the service. They charged my tenant $160.00 plus GST which is more than 10% above the quoted amount. I believe this is a violation of the Alberta Free Trading Act. I can't believe that a business would operate in this manner. I would have paid by credit card as agreed. They never said anything about the invoice having to be paid while they were still on site. They only stated in an email that they would call when done. That could mean anytime after the work was performed. I found this to be very unethical and unprofessional. I would never use this company again and would not recommend them to anyone. Using tactics as they did was completely unacceptable. This is what gives contractors a bad reputation. Do yourself a favor and find another contractor to replace your screens.