Land Registration charged on recent year rate

We purchased a land sometime in 2011-12 and applied for Patta registration for residential use to local municipal office. For all these years they never returned to our submissions and said they have lost files. Recently, based on old files, they demanded Patta fee as of 2017 rates. We are not aware of laws but certainly it’s a problem from Gov. side. Prices have gone quite high since 2012 for registration as well. How should we go about this. Can we ever be able to get the same old rates for registration. what we suppose to be doing to fix this issue.