That's definitely odd. We need a bit more info to better understand what's going on:
1. What phone model are you using?
2. What OS version do you have on the device?
3. Can you clarify if you see the number but not the name, or if you don't see a number nor a name displayed?
3. If you don't see both the name and the number, can you tell us what exactly is displayed when someone calls you?
Let us know and we'll take it from there.