Question about returning an iPhone

My 4S has been having some issues with the earpiece being silent on outgoing calls (apparently a pretty common problem). I called Apple, who says it's probably a hardware issue, and they are sending me a free replacement phone. Once I get it, I send back the defective one.

Question is: my current phone has a small hairline scratch on the front screen that has absolutely nothing to do with the reason why I'm returning it. Will Apple charge me any extra fees because the screen is scratched, even if it has nothing to do with the main problem?