Is reply of notice issued by property owners lawyer is required?

4 years ago

A shop rented by landlord 45 to 50 years ago to my grandfather and after 15 years ago in 1988 landlord sell the whole property including shop to Agarwal samaj samiti registered and trust continue the rent and start accpeting the rent from tenant. But from past five years i.e from 2014 they not accepting the rent but my father start depositing the rent to trusts bank account. On 6 October 2019 trust issue notice under section 106 of transfer of property act stating that pay the arrear of rent from 5 years and vacate the shop in 15 days. We have all proofs regarding rent payment through cheque in there bank account i.e bank statement. Please advice that reply of notice is required to sent and disclosing that rent is paid or any legal advice in favour of tenant so that not require to vacate the shop. Tenant has no other source of income.
The shop rented long years ago that time no agreement is made between trust and tenant i.e no written agreement exists.
What to do please advice...