Dealer ability to add or subtract funds from invester account

My first step into market was through a dealers platform, who manages my investment. Every transaction like IPO, OTC, etc.

Now that everything is done in thier platform are they allowed to add or deduct funds to / from my account as per SEBI and bank guidelines?

If someone is managing your investment and money, do you think SEBI guidelines is what will stop them if they want to actually withdraw it?

Thanks. I understood your point