Lodha Group — Transfer of flat

Address:

Mumbai City, Maharashtra, 400078

I booked a flat in Casa Eviva "G" Wing and after making payments worth 11 lacs, I was told that the project is getting delayed as they are facing some permission issues. They offerred me to move to Casa Eviva "Q" wing. They promised to take care of everything including the refund of stamp duty, bank ettc... Since I had already taken the loan and was paying interest, I thought of going ahead with the same.
Now after executing the fresh agreement, registering the same the Bank is not ready to accept the same stating Lodha Group has not intimated them about the same.
Whenever I call the Bank Guys, they say they are in talks with Lodaha higher authorities and will revert back but nothing is happening.
On the other hand I am getting calls every alternate date from Lodha Group, asking for the Payment.
Inspite of sharing the numbers of the PNB Housing Managers who are looking into my case, they keep telling me that they will be charging Interest for delayed payments. Please advise how to go about now?