My ex husband texts me almost daily

He is very calculated and very hard to deal with. We do not have a good relationship and the less I have to communicate the better i am. He has full access to what’s happening when the children are with me but I do not get the same courtesy when they’re with him. He just started using my past texts that he saved from years ago to bring back up and throw in my face. I have told him multiple times that I don’t feel comfortable texting and would rather communicate about the kids via telephone calls instead. He says he “wants a written record of conversations” I don’t feel like I have to do this. The only thing about communication that is written in my divorce decree is that “the children shall be allowed telephone access to each parent at reasonable times.” They’re 7 and 4 years old. I’ve never denied him a FaceTime or call even when he asks at inconvenient times. If anyone’s been through something similar I’d appreciate any tips or advice.