CONTACTS QUESTION!!
My sister and i share the same itunes account and i just looked at my phone and all of my contacts have been replaced by hers. How did this happen and how do i get mine back?
iPhone 4S, iOS 7.0.6
It happens when you share the same iCloud account. When you do, any data you both sync with the account (such as contacts) is merged. If your contacts then started being deleted from your phone, it's because she deleted them from hers, which deleted them from yours at the same time.
One of you needs to migrate to a new account so you are no longer sharing the same one. To do this, start by saving any photo stream photos that you want to keep to your camera roll (unless already there) by opening your my photo stream album, tapping Select, tapping the photos, tap the share icon (box with upward facing arrow), then tapping Save to Camera Roll. If you are syncing notes with iCloud that you want to keep, you'll need to open each of your notes and email them to yourself so you can later copy and paste the text into new notes created in your new account. Then go to Settings>iCloud, tap Delete Account (which only deletes it from this device, not from iCloud; the person keeping the account won't be effected by this), provide the password to turn off Find My iPhone and choose Keep on My iDevice when prompted . Then sign back in with a different Apple ID to create your new account and choose Merge to upload your data.
Once you are on separate accounts, you can each go to icoud.com and delete the other person's data from your account. Note: you can continue to share the same iTunes account. It does not need to be the same ID as your iCloud account.
Hopefully you have a backup of your contacts so you can restore them to your phone. If you don't, you still may be able to restore them from your iCloud backup by following the steps in Winston Churchill's user tip here: https://discussions.apple.com/docs/DOC-4841. Don't do this until your sister has moved to a different account though, or she will lose her contacts.