You should invest in a consultation with an experienced employment attorney, who will review your contract and determine whether you have a claim against your former employer for commissions and retaliation.
The information provided above is for general purposes only. It does not constitute legal advice or create an attorney-client relationship. Seek competent legal representation, because the facts of each case are different.
If the latest properly signed contract states that you are entitled to commissions, then your employer should pay you commissions.
I agree with the previous answer in that there are probably more issues with your situation than you suspect and a lawyer may help you to sort it out.
I have a few thoughts. Under the law, it is not terribly important whether the $ is called "tips" or a "commission" or a "bonus" -- what matters more is what it actually IS. Then, there are different rules about how that classification affects things depending on which law you are talking about. It is hard to say based on the info you have provided, but it sounds like you MAY have a breach of contract claim, an unpaid wages (i.e. unpaid commissions) claim, a violation of tip pooling rules.... there are a bunch of different things that MAY be at issue. ALSO, it is illegal for an employer to "retaliate" against you (like firing you) for doing something that is protected by law -- like laying claim to any wages you may be lawfully entitled to. Your situation may or may not qualify for that. While I wish I could give you a black and white answer, I'd need more info to really go through a proper analysis.
This is not legal advice. Consult with a lawyer about your particular situation.