Kotak Securities — opening a demat account without customers permission

Address:

400703

I have been receiving call from kotak mahindra bank for opening a demat account frequently and every time i answer them "not interested". But instead of considering their client choice they opened one without seeking any permission and on the top they have deducted 10750 inr. Now i don't know whom to approach. All i'm sure is this is illegal. I haven't signed any paper. They just did it by their own. I have heard other's experience with kotak mahindra and i'm not surprised much. People put money in back to save it from theft but my money is stolen from bank by it's guardian!