How can I protect myself from fraud ?

I invested through the Sharekipo app, which claims to be affiliated with Sharekhan Securities. I was allotted IPO shares randomly, exceeding my capacity, and they insisted on full payment. When I expressed my inability to pay, they mentioned they would cover the balance from a reserve fund and stated that I could return the shares after selling the IPO. They indicated that I could pay their amount after withdrawing some funds, but they insisted on full payment beforehand. If they do not allow the withdrawal, I risk losing the remaining funds. Additionally, while they claim to be associated with Sharekhan, there is no endorsement on the Sharekhan portal, raising concerns about the legitimacy of this operation. What should I do?