You should call them and tell them they owe you the money for the time you were working there. Then you should fax them a letter telling them they owe you the money. Then send a letter certified mail telling them to pay you or else you will get a lawyer. Then call one more time. If they don't pay you, contact an employment lawyer in your area who can help you get the unpaid money.
You may have a wage claim. Get an employment lawyer to look at it in detail.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.
While you may need to hire an attorney to assist you in getting paid, depending on the amount of money at issue, it may be more cost effective for you to contact the Texas Workforce Commission. There is information on their website about how to file a claim for unpaid wages you are owed. I've included a link to that page with this answer.