Denial of apprasial amount due to delay by company what should I do

I completed my one year in the company in March. I submitted my appraisal formalities in march itself. But there was delay in finalizing this appraisal by 3 months. In the mean time, I resigned for a better opportunity. Now company said, my apprasial has been upheld as I have resigned and serving the notice period. Why should I suffer and incur financial loss in wages, due to company delays...?? I would like to have your opinion on this. What should I do.. I have already talked to HR, Director n all... They say, its a policy, and when asked about the policy, they are not sharing it with me. What should I do?