Need advice on making phone calls

Need advice on making phone calls I have a usually mild stutter, and it usually only slightly worsens on the phone. But sometimes phone calls get so bad I have to hang up and just text the person I’m on the phone with. I only get blocks that severe over the phone, but I don’t feel like it’s a stress thing since it mostly happens with people close to me. Does anyone know the reason for this kind of situational stutter? How can I work on it?