I have a problem with a phone I bought and it is locked with iCloud, please act

Hello ~ So…if this is a second hand iPhone …I think that you have come up against the activation lock. If so you will not be able to unlock the device. We cannot help you nor can Apple. If this is the case you may try and return the iPhone for a refund or have the person remove the activation lock. If they cannot or will not …then the iPhone is of no use and you can recycle it responsibly. Take a look here for more info:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~