To see who is calling you is an optionnal service. You should pay to see who is calling you. There is a plan for that. Check this out with your provider.
it is caller line identification presentation
it's called, and should be stated on your invoice as CLIP
if you don't have CLIP you can't see who phones
if you don't have CLIP people can't see your number
in some countries it's mandatory to have CLIP
so on a new contract without CLIP this is understandable
but if you have an exsisting contract and this suddenly happened, then maybe it's your BB...
well this obviously doesn't seem like a problem with your phone then.
I would suggest calling your service provider and telling them what you want.
they should be more than willing to add it, seeing as they charge for it