Cors dinner refusing a refund for an over payment

I booked a kiddies party at Cors Dinners. I paid for 20 kids, however on the day of the party 12 kids were present to which I alerted the waiter that was attending to us and advised that the number of kids have reduced, he advised that I will have to take all the food that I paid for. I advised that I want a refund because my guests also bought food and there was no need to me to take food for 8 people home, I want a refund for the food that was not used.

I then spoke to the owner+***5 asking him for my money back, he keeps giving me a run around, it's been a month. Then he started threatening me with his lawyers. Such bad customer services, not impressed at all with the treatment received.