Rented Apartment Needs To Be Vacated

I have an apartment of 850 sq. ft. which is given on rent from last 20+ years to a company for commercial use. There was only one agreement that was made between us and the company representatives then. Now i am an legal owner of the property and i need the apartment to be vacated. The company does not use the place but is just using it as goods dumping place, saying that it will use it at a later stage. I do not have the initial agreement with me now, and no does the company have it. As i asked them to come to an new agreement they said they need a written communication for the same and are avoiding it from a long time. I feel that they might act funny if i send them an written communication for it. What should i do and what should my next step be?