Don't worry that she's upset, that's only a sign that she is into you. She's afraid that you're losing interest in her, and she's fighting back the only way she knows how, by throwing a temper-tantrum.
Wait a week before calling her, or until she calls you. When you call her or she calls you, act normal and happy. Don't apologize or explain yourself - you did nothing wrong. If she asks you why you didn't call her, tell her that it's disrespectful to hang up on someone, and that her behavior in not acceptable.
She might get more upset - hold your ground. Don't apologize, don't yell back, don't be rude. Show self-control. After a bit she'll realize that if she wants you, then she will have to show you more respect.
This is important, and I'm willing to bet you anything that if you went with her behavior, apologized, and given her all your attention without her putting in sufficient effort into the relationship, and showing you the same level of respect that you are showing to her, she will grow tired of you and drop you in a few months.
MotU
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"I tell you on behalf of women: there is not one of us who does not prefer a little rough handling to too much consideration. Men lose through blundering more hearts than virtue saves. The more timidity a lover shows with us, the more it concerns our pride to goad him on; the more respect he has for our resistance, the more respect we demand of him. We would willingly say to you men, 'Ah, in pity’s name do not suppose us to be so very virtuous; you are forcing us to have too much of it.'" - Ninon de l'Enclos