My toxic father

My dad left when I was little, he was abusive to my mother. He was never part of my life. When I was nine he tried to file for 50/50 custody. He only ended up getting supervised visitation to start with, but after months of not being consistent with his visits and me getting diagnosed with anxiety/depression the court battle ended and my mom remained with soul custody of my and my younger sister. Last year he tried to come back into my life and I gave him a chance, but he made up a lie about my mother and tried to manipulate me.

Recently I contacted him, not for a relationship but because I had some questions that only he could answer, like why he filed for custody so randomly. But somehow the phone call turned into him telling stories where he tries to tell me that my mother was the abusive one and she kept me away from him. Throughout this phone call he seems to have got it in his head that I want to try to have a relationship with him again, he told me I can’t call him and talk to him only to stop the relationship because I was being a tease. Its only been two days and already my anxiety has been through the roof. Every time my phone goes off I am afraid it’s him. I tried to convince myself that I could forgive him and build a relationship. But even if I would forgive him I don’t want a relationship. How do I cut ties? I wasn’t trying to have a relationship, and I feel bad just ending it. But I know it’s not good for me to keep the relationship.