Is there an easier way to purchase commercial ringtones and use them on an iPhone 4?
The trick should lie in converting your file to the appropriate format and renaming it so that it appears to be a regular ringtone file. (e.g. create an M4A file and change its extension from .m4a to .m4r). The top three links on a Google search are good tutorials if you like step-by-step instructions: https://www.google.es/search?rls=en&amp;q=%22ringtone%22+%22iphone%22+%22m4r%22

BTW, you can sync your iPhone over the air. Connect it to iTunes and look for the option "Sync with this iPhone over WiFi", first screen of the Summary/Info/Apps/Tones/Music/Movies/TV Shows/iTunes U/Books/Photos lineup.