Leave or stay with him?

My ex that I have gave now 3 chances with still remains on keeping his best friend who is a single woman in the picture. We got into a argument last night and he answers her phone call and talks with her. I was not around but I asked him about it. He was mad at her a couple weeks and told me he promised he would never talk with her again to save our relationship and have it go well since it has always been a issue for us. We got into a argument and she happens to call him during it and they talk he claims. I’m not comfortable with another woman calling and texting my boyfriend. He said she isn’t going any where and they are just friends. I’m not opposed of opposite sex friendships while in a relationship… let alone best friend who is female and single. Should I leave him or deal with it?
Leave or stay with him?
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