Q: icloud log in problem?

To change the iTunes ID, go to Settings>iTunes & App Stores, tap the ID, sign out, then sign back in with the ID you want to use.

To change your iCloud ID:

iOS 6:  Go to Settings>iCloud, tap Delete Account, then sign back in with the new ID.  This deletes the account and your iCloud data from your device, but not from iCloud.  Provided you are signing back into the same account, your iCloud data will reappear on your device when you sign back in.  To avoid losing photo stream photos, save them to your camera roll (if not already there) before deleting the account.  To do this, open your my photo stream album, tap Edit, tap the photos, tap Share, then tap Save to Camera Roll.

iOS 7: Go to Settings>iCloud, tap Delete Account, provide the password for the ID when prompted to turn off Find My iPhone, then sign back in with the ID you wish to use.  This deletes the account and your iCloud data from your device, but not from iCloud.  Provided you are signing back into the same account, your iCloud data will reappear on your device when you sign back in.  To avoid losing photo stream photos that are not in your camera roll, save them to your camera roll before deleting the account (open your my photo stream album, tap Select, tap the photos, tap the share icon -- box with upward facing arrow, then tap Save to Camera Roll).