if i bought a phone but its locked to owner what do i do?

Hello ~ Return it to the person that you bought it from or contact them and have them unlock it. If they cannot or will not unlock it you will never be able to use it . We cannot assist and neither will Apple .Take a look here..

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~

➢ Return a lost, locked iPhone. 📲