How can I calm the erflies when we talk on the phone?

So I'm on the brink of a serious relationship with a boy in my grade, and I'm really into him. But he said he wants to call me, and he did already but I was too scared to answer. I get very nervous talking to guys over the phone for some reason. He said he would call again after I "find my phone, because it's lost." How can I just calm down and talk to him normally?