I made the mistake of taking my car to a CT auto-centre once also (Burlington, Guelph Line). All I needed done was the right front sway-bar linkage replaced. I had checked online and confirmed the part that had broken loose before taking it in and I told them what was to be done. They put it up on the lift and looked at it for an hour - then came back to confirm it was the front right linkage and gave me a bill for close to $50 - they did NO WORK and did not have the part to fix it at that time. They called me a few days later to say they had the part in and would be able to replace the linkage and then gave me a completed cost for parts and labour. I went in later that day and had the work done and paid the bill in full. Two weeks later they called me up and said they mis-priced the linkage and that I owed them another $100. I told them (as per Consumer rights) that - I was quoted a price - I was billed that price - and I paid that price the same day - I owe nothing further - this was their mistake not mine. They sent me a letter threatening me with trespassing if I should ever grace their store again. How many other companies would try that stunt? Most realise that if they make a pricing error - that's too bad - they are required by law to give the lower price.
I spoke with CT h/o and they said this was not their doing - it was between me and the specified store as they are independently owned. Good way to wash their hands of the issue.