Pay protection of govt bank employee on further joining at c

Sir,

I was working with a Govt Bank and recently been selected to a CPSE . On advertisement and before joining it was confirmed that my pay protection will be done as per DEP guideline. Now after joining they are telling no pay parity is their between Govt Banks and CPSE , so it would not be possible to give pay protection. 

I would like to get legal assistance in above case , and if any earlier judgment is given than it will help me rather than fighting with management

Regards

Ranjan Kumar