How to call off the wedding when the reception hall is already booked for November?

Tell your parents tonight that the wedding cannot happen. Do not wait for a weekend or a family meeting with extended relatives. Sit down with the people who raised you, look them in the eye, and say that you met him twice, tried to make it work in your head, but realized today that marrying him is a mistake you cannot fix later. You will face immediate panic about the November dates, the caterer advance, and what the neighbors will say. Let them shout or cry. Your job is to stay entirely firm on the core fact that you are stopping the process right now. Once your parents understand you will not walk down that aisle, ask them to handle calling his family to break the engagement immediately. Do not try to explain your internal realization to his relatives or soften the blow with vague excuses about timing. Clean breaks require sharp edges. The money lost on the reception hall and the catering advance is a heavy price to pay, but it is entirely recoverable compared to the cost of a life spent undoing a rushed marriage. Your family will absorb the social friction within a few weeks, and the talk will eventually fade. Stand your ground tonight, take the full weight of the immediate anger, and protect your future from a commitment you already know is wrong.