Termination of employment

I left my previous organization without full and final settlement, as they were not willing to leave me without serving the notice period. My offer letter states: "Termination of Employment: This appointment can be terminated by you by giving three month notice compulsory. Similarly, this appointment can be terminated by the company by giving three months notice or against salary (fixed CTC less retiral benefits) in lieu thereof."

There is nowhere written that I've to pay 3 months CTC if I leave before. Now they are forcing me to pay 3 months CTC or they will take legal action. Meanwhile they passed a handbook for employee which states you have to pay 3 months CTC amount which is not signed by me.