Can't log out of someone else's find my iphone without their icloud password I just got a previously used iphone from my work. However, the previous owner is still logged into their icloud account. Whenever I try to logout of their account it requires their icloud password to log out of their find my iphone. Even when I try to wipe the entire phone it requires the password, what should I do?
Contact the pervious owner and ask them to log into iCloud themselves and release this phone. 


https://support.apple.com/kb/PH2702


Failing that, ask if work has this device enrolled in an MDM or to contact Apple to validate via the serial number that the device is not owned by a consumer or different company. In that case, your IT department can bypass this activation lock. If work has an HR department, they can request / require the previous owner to follow Apple's steps to release the device. Legal could bill the past employee for the replacement cost. 


How secure is Activation Lock on iOS 7 (and later)?


You probably need to just turn the device in or wait it out since bypassing the lock isn't viable.