How to make an Iphone 4s unfixable by apple?

So this is a horrible question to ask considering I couldent find anything on the web about it, but how would yo do it? There's a few things wrong with my Iphone, but all are completly fixable, and i'm sending it in soon. I've already made an call and their sending me the box to put it in. I've been looking for some kind of loop whole for an upgrade of some sort considering right now I can't afford one, the only reason why I want one is because of the fact the one I have is an 8 GB 4s. But thebottom line is, how do you make it unfixable by the company, theyve already said if they can't fix it their going to send me a new one, and considering they don't manufacture the Iphone 4s.s anymore ill get the upgrade I want.

There si no way to do that without leaving traces their engineers know to look for, And if yo do that they will consider it fraud and will either charge you for their time, and refuse to return it till you pay the FULL bill as it will no longer be covered, or they could prosecute for fraud.