Oh, I've been there. Hating the sound of your own voice on calls is so common, but it's also something you can work through.
Standing up genuinely helps-forces you to breathe deeper and project. I always use a headset so I can gesture naturally. Those hand movements? They absolutely come through in your tone. if you'd wave your hands talking to a mate, do it on the call. Your body language changes your voice.
Preparation makes a massive difference too. Before any call, I skim the last email, any notes, and maybe a relevant bit of news. That way I've got something real to lead with, not just a rehearsed pitch.
Nobody wakes up brilliant at this. Sales voice is trained, not born. Give yourself permission to be awkward for a while.