Hello ~ That is the activation lock. If the person/persons that you bought the iPhone from cannot or will not remove it …the iPhone is basically useless to you. If they cannot/will not remove it…return it and get your money back. We cannot help remove it nor can 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~