Hate/scared to talk on the phone, and talking face to face with strangers.?

I'm a 14 year old female, when I'm around my friends I'm extremely talkative and crazy. But when it comes to talking or even being around a person I don't know, I get really scared and quiet and try to avoid the situation at all costs. EX. I won't pay at a grocery store, order my own food at a restuant ( i make my parents) or ask someone for assitance and even when i went to an "open court" for tennis during the summer, i didn't know any of the people and refused to get out of the car, even though i wanted to play extremly bad. All my friends, and my family make fun of me for it and i can't do anything about it. I break down and cry, hide, or get really really nervous and try to run away if I'm put in these situations. I'm also the same way on a phone, i won't pick it up unless the caller ID is my parents or my friends. For school i was forced to call 10 people. ( 7th graders parents to let them know how they were doing in shcool) and i cried/panicked for an hour. One of my friends fianlly coaxed me into doing it, but the two people i called couldn't understand me becuase i was stuttering and kept loosing focus of what i was saying. I will only txt strangers now, no matter what. Can someone please help me, I don't know what to do anymore, and my parents are always upset with me because of this. ANy suggestions will help! ( maybe) And just saying "get over it" isn't helpful, because i mentally can't.