Agree to what? The employees are required to follow Apple's policies. You will get what they are required to replace your phone with.
I don't know why you're quite this fixated on getting a brand new phone. You brought in a used phone. Why should the replacement be brand new? A new device they could have sold to someone else?
If you bought a brand new car with a 5 year bumper to bumper warranty, and the engine had a catastrophic failure at the three year mark, which of these do you think the company would do?
- Replace the engine.
- Give you another brand new car, which would a model three years newer than what you had.
No company that wants to stay in business just hands out brand new products to replace defective or broken ones.