TC in North York

I signed a contract and paid the deposit to replace a section of my main drain both inside and outside the house. After breaking up the floor inside the sales came by and told me I had to pay extra because now the pipe outside was "too deep" so he pretty much forced me to pay an extra thousand dollar cash or else they won't continue to fix the drain. I had already paid a deposit and they already broke the floor and everything inside so what other options do I have? I paid the extra in cash as they suggested but afterwards when I called the office there was no record of that extra amount being charged/paid and when I asked further the sales refused to provide me with a receipt for the extra cash that I paid so I highly suspect that he just pocketed the extra cash which I shouldn't have had to pay to begin with. It's unfortunate that the sales was being unethical and forced you to pay extra halfway into the job as I had high expectation of this company after getting quotes from various places. The job performed was decent but I wouldn't want to deal with the hassle of someone trying to pull tricks halfway into the job for extra money again.