Customer has been promising to pay and hasn't can we go ahead and lien them
You really should retain a construction attorney to review and evaluate your legal position based on the contract and pertinent documents. The right to be entitled to file a mechanic's lien is set out in Texas Property Code Chapter 53, and you really need to make sure that if you file a lien, you have properly and appropriately done so.
Filing an invalid lien could subject you to liability under the Texas Fraudulent Lien Act, and you could be liable for statutory damages of $10,000, or actual damages, whichever is greater, plus attorney's fees. Facing such a claim would add insult to injury.
Whether or not you have a right to file a mechanic's lien will depend on a host of factors, including without limitation, the nature of the project (commercial, residential, homestead, etc.), where you are on the pecking order (original contractor with a contract directly with the owner or the owner's agent, or subcontractor, or what), whether you provided the notices required under Chapter 53 of the Texas Property Code, when you performed the work for which you have not been paid, whether the project has been completed, and other factors.
Again, retain a construction attorney to evaluate your legal situation and to provide advice.