Cheated by housing finance (home loan)

Sir i am only 20year old.. Due to lack of experience... I bought a ground floor flat by my own mony..i have taken loan of 7 lakh from Supreme housing finance. I was very happy that i got good deal bt later i got to know that ground floor is unauthorized in this colony.. There is 0 resale value of my flat... Now please help me can i take ligal action against bank? as they have done proper legal, technical, valuation proses then why they didn't rejected my loan, i was thinking that if bank is giving the loan thats mean property is ok... I am really very tensed now plzz help... 7982615005