Final answer:
The unethical practice in question is called breakpoint selling, where an investor is not informed about the opportunity to pay lower sales charges on mutual funds by investing just a bit more to reach a breakpoint discount.
Step-by-step explanation:
The violation of selling mutual fund shares just below the breakpoint where the customer would qualify for lower sales charges and not informing the customer that they may qualify for lower sales charges is called breakpoint selling. This unethical practice takes advantage of the investor's lack of knowledge about the fund's pricing structure. Investment firms and advisors have a legal obligation to inform investors about opportunities to pay lower sales charges, including the availability of breakpoint discounts.