If you are not being compensated fairly, male or female, find a new job. A company is in business (with a few exceptions) to make money and will reduce costs wherever possible. If they are not treating you fairly, find a new employer who will do so. Same thing goes with Walmart, if you don't like their employment practices, go elsewhere, no one is forcing you to work there. They do not owe you a job, no one owes it to you to employ you. You have to prove yourself as an employee, no matter what the gender. If you are that good and not advancing, go find suitable employment else where.

Also, just by making something illegal does not fix the problem.