What to do institution to leave our food outlet built in the premises

We have a food outlet in one of the reputed institution which was built by us 5 years back on the area assigned by the institution for which we spent a lot of money. There are 14 outlets in that food court area. We have no documents regarding the contact and no receipt of rent and maintenance was given to us. Presently the rent is 20,500 which is always paid by cash. 12 days earlier they told all outlet owners verbally to vacate the place by 30th June. They informed that they have given that place to someone else and he is asking for Rs 75000 and other charges. Kindly advise what should be done in this case.