I have an Iphone 5s locked to the activation screen?

I bought an Iphone 5s off an Facebook buy swap page and then I reset it and its been locked to the previous owner who I no longer have contact with? There must be a FREE way to get permanently pass this lock?

Added (1). how do i do it

No there isn't. That is a security feature. Sounds like you may have been ripped off. You should try to get your money back in whatever way you can.