If you're a Pi Phi, feel free to PM me and I can walk you through what you need to do, and what some of your options/consequences could be. I have several pledge class sisters or women I have advised who are now, a few years after resigning, asking to be reinstated as alumna members - make sure you have thought through not just what you'll feel now, but what you'll feel next month, next year, in 5 years.
Otherwise, talk to pledge educator, chapter president, or secretary/VP Admin. If you would feel more comfortable talking to an alum advisor, you should be able to get ahold of their information.

If you are a Chi Omega, early alum status is not common. Contact an alum advisor or Exec HQ if you have extenuating circumstances.
If you are transferring to another university that has a Chi O chapter, you are not required to affiliate -- it's optional.

If you want to drop out, contact your chapter president or chapter advisor to discuss this procedure. If you're thinking about transferring to another school, this seems to be more to do with being generally unhappy and no sorority is going to be "right" for you until you are right with yourself. Wishing you the best as you sort everything out. College is a tough time and you're figuring a lot of stuff out. Sorority life isn't for everyone, and even for those involved its not always sunshine and rainbows. Being in an organization with women is HARD. If you're really sure it's not right for you, cut your losses and move on. But as with anything, if you aren't invested in something with a positive attitude and making an effort to get to know people, you're going to be miserable. That's just life in general.