Hello rythymace!
This isn't a known issue for the Prism II. Just to make sure, these are the steps you're following?
Change ringtone for calls from one contact
- Transfer the sound file to the Music folder on your device.
- From any Home screen, tap the People icon.
- Navigate to and select the contact you want to set a ringtone for.
- Tap the Edit icon.
- Scroll down to and tap Add another field.
- Tap Ringtone.
- Tap Select from music.
- Select the desired sound file, and then tap OK.
Ringtones & notifications: T-Mobile Prism II
Please let us know so we can provide a prompt reply since you only have a few days left within your Buyer's Remorse period.