dududu...what kind of phone do you have? I ask because if you have one of certain phone types there are backdoors you can go through to get stuff done. Motorola and certain LG (and a few samsung) phones are currently about the best ones to do stuff with in terms of adding ringers, music, wallpapers, videos for free.
even less phones than that are currently flashable to other carrier's firmwares. but you have to do LOTS of research if you are going to attempt to do that. And keep in mind that with certain flashes you may GAIN certain things, but you will also LOSE certain things.