Many yrs. ago, I accepted a job from an MSC to open an account; there was a list of three or four from which to choose. I decided a CD would be best for me, completed the report and awaited my pay. I am guessing I did not contact the company until two months had elapsed. My inquiry was quickly answered with the explanation I would not be paid due to scheduler error, as a CD was not acceptable. My response was that their scheduler's error was not my concern and that if my pay were not forthcoming, I would seek the assistance of my new bank, who was also their client. My money quickly arrived that day by PayPal, even though they had always paid me by check.
The problem with contacting a client, is that you ruin the relationship and, as has been noted, you violate your agreement. but I have never, for a second, regretted my position. In the event anyone is wondering, I immediately became a shopping persona non grata with that company.