Builder gave me letter that I cannot have possession of shop

I purchased a shop from Mr A in resale who had paid 90% of the payment to builder & I paid balance amount Mr A had signed a allotment of shop space agreement with the builder and clause no 6 stated that flat buyers agreement will be executed in companys standard form The builder gave me a letter stating that possession of the shop was given to me on 01.12.1977 & is owned by me The shop buyer agreement which was to be executed in builders standard form was not executed Delhi apartment act 1986 section 4 states What is my status regarding this purchase