The only way to get over it is to talk more on the phone. Even if you can't say anything, just face it . Once you develop the courage the fear will slowly start diminishing. I know it's not easy as it sounds. I hate calls too and try to text or mail as much as possible. Can't say a single letter sometimes and i just hang up whenever i feel like it's not gonna come out. But try to keep the fear away and just face it . All the best !!!