Can't say "hello" on the phone

Can't say "hello" on the phone So, for a while now almost everytime I get phone calls from unknown numbers, I freeze and cannot say "hello". I feel like I get scared by the phone call, like a similar feeling to if somebody jump scares you. I think this might be because of something to do in my childhood, but now I cannot afford to freeze up like this as I've applied for jobs. Luckily the phone calls are usually spam and cold callers but if it's a reply for my application, I just can't afford to do this. Any help or responses would be appreciated!