How do I find restricted phone number and trace it from my mobile phone?

Friends,

Is there way I can find who is calling to me when I get call from restricted number. I am receiving harassing call from this number which is restricted and I am going nuts. I have called verizon and they advised me to change my phone number but i can't change my phone number but want to know who is making fun me and harrassing me.

Can anyone tell me how do I trace who is calling me , it is really causing problem for me. but if I change number i will face even more problem.

i heard that one can do few things to find out restricted number who is calling.