Parkdean Resorts complaint: Order Pay App

Hello!
I ordered food from our caravan to eat at the table in Todber Valley Holiday park’s restaurant where we’d eaten the night before.
The food came and the staff said we’d paid full price because I’d used the app.
They said the manageress would be coming in later and they would ask her to refund the difference as it was ‘Eat out to Help Out” during August on a Wednesday night and this was clearly stated on the app itself.
I heard nothing and chased up the next day (Thursday). The head chef advised us to speak to the manageress, Charlotte.
Friday we were leaving so I went to the sales office to speak to her in person but she wasn’t in. The receptionist sent Charlotte an email with full details.
I called on Sunday, no answer. I called this Tuesday and left another message with the receptionist as Charlotte was in a meeting.
I’ve called today and left another message.
I do feel I’m being intentionally fobbed off.

The barrestaurant staff were lovely but the holiday itself turned into a nightmare due to car issues. This overpayment in food and the inconvenience in chasing this up is unhelpful.
Eating out to help out didn’t help us.