Phone upgrade question!!!?

I have a 2 years contract with AT&T and its been a year now and I'm eligible for an upgrade. My father mentioned that upon upgrading I'm actually signing for another 2 years. So is he right? Am I signing for another 2 years if I upgrade my phone? I have a basic phone and I'm wanting to get a smartphone. Does that mean I have to sign up for another 2 years? Doesn't sound right to me...