The landlord refuses to return the advance security deposit

I & my brother were asked by the landlord via call/WhatsApp chat on Sep 15, 2020, to vacate the room in a Noida society flat till 15 Oct 2020. There are a total of 4 people in flat & he has asked only us to vacate. The reason is we are going to vacate it by December 2020 and he has found a replacement right now only. The rent agreement for 11 months was from June 2019 - May 2020 & wasn't renewed due to the pandemic and lockdowns. I and my brother have been in Jalandhar since mid-March 2020. We have already paid Sep 2020 rent. We told him that we will vacate by 30th September & he should return the deposit. He refuses to return & hasn't deposited flat maintenance for Sep 2020 with society. We would take a non-essential journey of 1000+ km along with parents for a couple of days just for shifting during COVID-19. Since June 2020, he raised the rent by 400 during lockdown & we are paying the increased amount as well. One of the 4 boys would collect the amount of 17400 (Rent=15000 & Maintenance=2400) & transfer 1500 rent to the landlord and submit 2400 as maintenance with the society. We doubt he will give a NOC. We plan to extend stay for 1 month without paying rent to compensate for deposit. Also, the rent agreement and other documents haven't been deposited by the owner with the society. Please advise if I am correct in not paying the rent for October to compensate for the rent or if there are any other options.