They booked the banquet hall for November without telling us. How do I say no now?

You need to call the venue yourself today and tell them you are not ready to confirm the booking, or ask your parents to cancel it immediately before the deposit becomes non-refundable. Your mother is operating on the assumption that compatibility follows commitment, but two coffee dates are not enough time to decide on a lifetime, and locking in a date creates an artificial momentum that makes it much harder to say no later. Admitting that you do not know him yet will trigger an immediate emotional reaction at home, and you are going to have to sit through the shouting and the accusations of wasting money without backing down. Say something specific to your parents like, I cannot let you spend money on a hall for November when I barely know him, and we need to pause this process until we have spent real time together. The financial loss of a small deposit is negligible compared to the cost and social fallout of calling off a wedding three months from now because you rushed past your own doubts. If your parents refuse to handle the venue, you have to be the one who makes the uncomfortable call to the manager to stop the paperwork. Stand your ground on the timeline, because once the invitations go out, the pressure to conform will multiply exponentially.