vodafone connection

I have taken vodafone connection approx 3 years back. My phone no is 9732583566. While taking my connection I have given my all the required documents. Now, my SIM is not working. I intimated to customer care. They are saying that this existing vodafone number does not belong to me. So, please give me suggestions so that I can get my old number again, because that number is vey important to me.