Need advice about general contractor harassing with mechanic lien placement

Background: I bought a house in Denton county, Texas in the name of LLC (I am the sole owner). Got a general contractor to start remodeling work. There is no written contract. Contractor started working and invoicing each week for completed work. I was shocked by cost contractors invoice each week as it was far more than what we discussed and agreed. He continued that and inspite of the raising price I paid for 3 invoices and then for 4th I clearly checked before he did the work, yet he again invoiced with 3 times more price. This time I said I will pay as we agreed and he started threatening me with mechanic lien. I need help with how to navigate this. The discrepancy of money is about $6000 at this point. I have sent him an email stating about the unauthorized work he did and bad quality of work. What do I need to do to make sure I am protected here?