How to decline business deal?

I'm starting a business and I'm looking for another business to work with. I've come to see that they are no longer beneficial to my business. They have helped me accomplish some goals, but was never agreed that it was part of the deal. I asked for help and they accepted to help me. We came up with one final agreement, but I still want to opt out. Nothing has been writing, it's all been verbal. I'm in Texas, I believe that verbal agreements are valid in court.

I respectfully declined their offer but they insisted that I do business with them. Once they saw that I wasn't budging they threatened to defame my name and business, talk to my other contractors and exploit me, accused me of being greedy, challenged my knowledge in business, used profanity, promised me that I would not succeed, and that they were going to sue me for wasting their time.

Up to this point they have not done any official work for me. They have not done anything that is part of the deal. They helped me interview candidates and call potential clients, but that was never defined to be part of the contract.

We are going to have a final meeting this week and I want to decline the final offer. Am I able to to do this? Again, nothing has been in writing.