The good doctor brings up a very valid comment....................
Modern day business ethics has gone down the tubes at supersonic speeds..... For instance.... A good friend runs the FBO here, he is VERY hands on and looks at EVERY bill being presented to accounts payable to check for accuracy and fraud........ In the last few months he has noticed a HUGE increase in " questionable" charges and he investigates each one to confirm they are valid and on the level........ Especially credit card statements......
Seems the newest scam going is to run a charge through hoping the accounting office will just pay the charge without questioning the accuracy of it.... They assume some low level AP/AR clerk will just "cut a check" and I bet they get paid 99% of the time... They play the odds of NOT getting caught and are milking businesses out of ALOT of cash.....
DR Bruce has now been scammed by two name brand rental car companies and you can bet your a$$ this was NOT a accident..





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IMHO. YMMV...
Ok, I gotta call time out on this, and Bruce as well. It's been since the dawn of the first coin of the realm that fraudulent billing has been going on. Does the credit card make it maybe easier to get duped? Quite possibly! Most of the common fraud on ancient times was from internal graft, which actually became quite common, and one of the reasons why bookkeepers(only base word in English with triple double letters) were paid so poorly. It was expected that they would keep a little of a transaction for themselves. In fact the term 'clip job' comes from the old method of using a small knife to snip off a piece of a coin. Really, the tort system has been around since the writing of the code of Hammurabi. Maybe they paid off in goats, or beans, but they had to pay off. The end of that internal stuff came with the advent of double entry accounting methods.
I've run several small business. It's rare for a small business to be run on the basis of lawsuit avoidance. That may not be true of the medical profession which has become a specific target for theft by tort, but by and large, most small businesses avoid lawsuits rather easily. By being honest! Of course, if one of the OPs clients thinks he stole proprietary info and sold it, they can take it to court. Proof of a fraud is damn hard, and has a serious high standard of proof. What's more, given that lawyers only work for money, they have to have a pot at the end of the rainbow. Many sole proprietors don't carry much in the way of recovery assets. Houses, cars, furniture, and even jewelry is exempt from collection actions.
I've been a landlord for almost 30 years. In all that time, in a very litigious state, I've been to court a total of 5 times. I won 3, tied 1 and the one I lost was more costly to defend when I lived in TX than it was to go fight it. If I'm doing something wrong, I should worry about being sued. If I or the OP isn't doing something wrong, then don't worry about it.
I rent cars literally 2-3 times a week for 15 years. I'm pretty good at it. Aside from one billing error by Avis in Houston and one try by Enterprise to jack up the rate I've never had a problem. I think it's because the vendor knows that I check on my bills, and I check on the cars I rent being checked back in. Even if I have to make 3 or 4 phone calls to the place that's on the contract, I KNOW the status within 12 hours of returning a car. Always, every time.
The OP is good at what he does. If his client thinks he can have the service exclusively, then they should pay for that advantage. If it were me, I'd go to the client tomorrow and tell them that Gina at XYZ has expressed an interest in my services. If that's going to be a problem, then sit down and discuss parameters. They may terminate his contract on the spot, and if they do, then his expertise will go to the competition. Stupid clients deserve to lose money.