Assuming you have the current version of iOS on your phone, it’s simple to assign custom tones to phone numbers, you just go into their contact info in the Address book app and tap the “ringtone” box to select custom ringtones and assigned text tones (from the default list)
However, you can’t use custom-made text tones without jailbreaking.
@Lightlyseared just used that method and it worked great for the ringtone, I’m gonna have to shorten my SMS tone because at 43 seconds it 3 seconds too long for the iPhone.