Vodafone — Bad after sales service

I Purchased a vodafone (Model VF 226) handset from, Vodafone store, Shop No.8, Shanti Shikara Commercial Complx, Somajiguda, Hyderabad on 31.03.09. The Display of the phone is damaged now and I am calling to the executives of the Store contineously since 16th May 2009, and they are not responding and always they are taking the same excuse that we do not have stock to change the display and they will revert within one hour.
Since past one week they have never called back from there end.
Kindly suggest me what to do?