Stilt parking not allotment

We are staying in Mumbai under BMC municipal limits, we are staying in flat purchased from the builder directly along with a stilt parking. For the stilt parking he has issued allotment on his letter head along with the stilt parking number. Since the time we are staying around 2010 the society is not allowing and even not allotted us the stilt parking, the society has given us an open parking only. On a continues follow up by the builder and the society thy are still not allowing us, they say that society didn’t get any instruction for the builder. Post given formal letters along with the allotment letter of the stilt parking they are not considering it as they say it also has to come from the developer two as there were two companies involved in developing the building, Builder and Developer both are two different partners. Currently the developer hols 90% of the stilt parking premises. But in the 10 % which is been hold by the builder in that also we are not being given any preference to park the car and now due to some fund issue which the builder was not giving to the society , society has decided to auction the stilt parking and get the dues cleared against the fund. Looking forward for your legal advice, suggestion