vacating grandmothers property in which i do business

i run a printing press in a area of 8 ft x10 ft in my grandmothers property total area 1200 sq ft. My grandmother when she was alive had given consent in the bank for using the entire ground floor for press on no rent basis with a letter in the bank as i had financed a machine when she was alive. I have original of the rental agreement with my grandmothers signature Now out of the 8 rooms in the ground floor i use only 1 room for press as i wanted to avoid conflict. The property as i had read the will was bought using her stree dhan by my grandmother. When she was alive there a will made for transfer of property to my father. Now my sisters and father want me to vacated the place. i pay 1200 p.m. transferred from my business a/c to my mothers a/c as rental value for the occupied area as agreed verbally. what are my options and what do i do to continue working over there or get a share if they want to sell the property or see that they dont sell property without my consent