Rent deposit when landlord changes

The new owner is making things difficult, and you're unsure about your next steps. You can start by reviewing your rent agreement to understand your rights and the terms of the deposit. 

Make a list of the deductions the new owner is making and prepare a response.

You can try negotiating with the new owner, referencing the agreement and any communication you've had. If that doesn't work, 

you might consider seeking help from a local consumer protection organization or a lawyer who can guide you on the best course of action.

They can help you understand the laws in your area and represent you if needed. 

Show rent agreement with relevant records to a local prudent lawyer for proper analyses of facts/ document, professional advise and necessary prceeding.

I went to consumer helpline ...they said the rent agreement has old owner name and new owner name is not anywhare and raised a complaint against him for his response......but he did not reply and consumer helpline waited for one month and did nothing....after one month theys said Go to Consumer court and for which they did not help....

Should I file case against old or new owner because new owner name is not in the rent agreement ?

Also can the new owner deduct the increase rent of 10% which the old owner did not ask?

You have paid the deposit to the old owner and as you have not entered into the rental agreement with the new owner, you have a claim with the old owner only hence you better issue a legal demand notice to the previous owner and then drag him to court for recovery.

He cannot deny return of the deposit because it was his fault to not to obtain a written receipt from the current owner in this regard neither he involved you in this.

can the owner deduct the increase rent of 10% which the he did not ask when due and thatswhy I continued to stay in that flat....?

The owner cannot demand the enhanced rent at this stage while your tenancy has already been terminated and also when he never raised this issue during the currency of the tenancy.

Attornment  letter must be submitted to tenant, only thereafter tenant should pay new landlord. Applicable for Bombay 

Your case is against the old owner. The old owner and new owner have to inform you that the ownership had changed. The new owner had to give you notice to increase the rent. You need pay only rent at old rate during the notice period and if you choose to vacate the flat you need not pay the new rate at all.

You file a consumer case against both the landlords with the old owner as the first opposite party and the new owner as the second opposite. Your complaint should take objection to the manner in which the ownership was changed arbitrarily without taking you into account. You should claim your deposit in full with interest in the event of delay from the old owner and refund of all amounts paid to the new owner less rent at the old rate for the period before you vacated the flat.

If the new owner refuses to refund amount already paid you should state the amount was paid under coersion. 

If your demands are clear you will win the case.