I have always been able to allocate a ringtone to a contact on other older phones, but does anybody know how to do on the Nokia Lumia 635?
Try this:
1. On Start button, tap People Tile, then swipe over to Contacts.
2. Tap the contact you want to change.
3. Tap Edit icon, then do one or both of the following:
-Tap Ringtone, then tap the ringtone you want to assign.
- Tap Text alert tone, then tap the alert or custom sound you want to assign for text messages.
Let me know if that works.