i bought the iPhone from someone but can not contact them so i have no way of unlocking the phone

you will need to contact the previous owner to have them log out of iCloud or go to iCloud.com/Find My Phone and erase the device, then remove it from their account. If you can’t do that, the device is useless. Apple will not unlock it unless you have a copy of the original purchase receipt with the serial number on it.

Activation Lock - Turn off Find My iPhone