Problems that my Phone could have that would warrant a replacement?

I recently quit my Job and so I need to tighten the belt one way I plan to do this is reduce my phone bill, so I will stop paying for the insurance, before I do this I would like to get a new phone (just because it's less likely a new phone will have problems because this one has been dropped a couple times ad what not) this morning I came in and I said the texting was inpresice (and it was a little) and they had me change the operating system (and it fixed the problem BUT I CAN'T STAND IOS 8.0.0) and it has made texting easier... there's nothing wrong with the phone I just want them to give me a new iPhone 5 for a perfectly functioning iPhone 5 for giving them an extra $10 for NOTHING...

what's a problem that I could swaer it has that I can't prove that they would be willing to replace it for?

I have sprint

First of all, check if your still under warranty. You can probably check on your carriers website using your IMEI number. Assuming your ARE under warranty...its usually software/internal issues that they can deal with. Things like water damage or cracked or scratched phone will not be covered.