My question involves labor and employment law for the state of: Texas

I have resigned from my position 3 months ago. I had no employment agreement at all, no non-compete, non-disclosure, etc.
I am directly competing with my previous employer for the customers. I've learnt over the last 3 months, that he is spreading rumors, that I have non-compete agreement with him, and if the customers make business with me, he will sue them. What legal action can I take?