if the iCloud account his your client iCloud account he/she should call AppleCare for them to help reset the password, if the iCloud account is from a dead relative they have to provide proof of ownership and proof of deceased relative, if all checks ok they will help your customer.
if he/she refuses to do it you should suspect that the iPhone is stollen or found and he/she just wants to bypass the real owner iCloud block.
if he/she refuses to do it you should suspect that the iPhone is stollen or found and he/she just wants to bypass the real owner iCloud block.
