In regards to learn to not giving a fuck, since the phone is high pressure for you, perhaps practice not giving a fuck in medium pressure situations. It then may be easier to do that for the phone. The key is afterwards, just let those negative thoughts pass. Do not dwell. If this proves difficult, try being really proud of yourself that you used the phone, then move on with your day. The whole phone thing at work is hard and I struggled for years. Initially, I made calls from another area. That's just more avoidance. What finally did it for me was forcing myself to use the phone a whole lot more. Like instead of email, calling the person instead. Its tough, but it will get easier. You got this.