Air India - Compensation for the travel being delayed for 8 hrs

I’ve booked a connecting flight from Delhi to Chennai via Mumbai.. At Mumbai airport the flight authorities hasn’t allowed us to go back to airport after landing due to rain and I’ve informed them regarding the connecting flight and they have asssured me that * other members are there in flight who also wants to board on same air India flight and asked me to not to worry as the flight would wait fr me and as soon as I reached there was some staff waiting fr me and even he told me that flight is there and asked me to follow him and took me to support staff n left without saying a word
The support staff told me “ Sry mam the flight has already left” at **:** Pm and asked me to take the next flight which was scheduled at *:**Am. I got frustrated of their behaviour for lying me … instead they shud hv told that flight left before hand
I refused to take the flight cause I wanted to reach another destination from Chennai which is Karaikal and is ** hrs far from Chennai in order to attend my convocation at *pm which is very important for me… and I asked them how can u do so without prior information and didn’t accepted after which the air India manager of Mumbai airport assured me of my rental car compensation and the tickets after which I’ve accepted to take the next connecting flight which was also delayed by * hours and now wen I wrote an email to the concerned authority they were declining my compensation saying that they have provided me another flight at next day * am in the morning… I was waiting from night **:** pm to mng * Am and I’ve complained by saying that providing another flight that tooo after making me wait for so long was not equals to compensation…. I’ve paid my money **,*** bucks for flight and so they hv to provide me another flight for not letting us in into the airport and the flight…. How this will be equals to compensation
I request to take an strict action against the staff behaviour and support services for doing so…