Pay fixation on promotion on deputation from IDA pattern to 7th CPC

I was appointed in PSU on pay scale of [deleted] (LEVEL-4 IN PSU) and then went on deputation in pay level-[deleted]. The last pay drawn in PSU is A. Basic 20160 B. DA 3468 (17.20% of A) C. HRA 4838 (24% of A) D. Perks 7056 (35% of A) TOTAL 35522/- Pay fix on deputation as i opted deputation pay A Basic pay 25500 B DA 9214 C HRA 7317 D TA 4824 E Medical 2310 TOTAL 50765. Now m promoted in PSU in pay scale [deleted] (level-6) with basic pay 22000/- My question is can there be grade pay increase in deputation as m promoted in parent department from level-4 to level-6. In deputation organization my basic pay is already 27100 now so they are saying there will be no pay protection of any increment as we are already paying higher basic pay.