How to change land type in porcha

Hello, I have a land at north dumdum. I didnt check porcha before buying it but after buying that I found that the land type is wriiten pond in porcha but in dalil it is written land. But there in no pond in that land. It's a little low land. Now I want to know how can I change the porcha from pond to land and what it cost. It will be very helpful if you please suggest me. Thanks.