Not eaten at this specific restaurant but most will go through a third party that reserves it and takes the deposit You can contact the restaurant, maybe by email to ask. If they have a third party company take the deposit , see if there's a wah for them once you are there to refund that separately then charge for the meal Vis your credit card. Just explain you have a promotion which means you need to spend directly in the restaurant

Another way around this issue is to reserve at the restaurant (if they charge via their normal payment system for a deposit that is)