I have another device iPhone 4S locked iCloud account to another person and the person does not know him

You need to contact the previous owner of the device in order to get the control over your device. If you do not know the previous owner, you won't be able to change iCloud settings and you won't be able to unlock the device. Please see also the following article which explains all the options you have: http://support.apple.com/kb/TS4515?viewlocale=en_US&locale=en_US