Wagamama complaint: Poor customer service, cold food and missing item

Ordered a click and collect.
Part of the order was vegan k-dogs. The website doesn’t have an option to customise any part of any order. We have to have them without the spicy sauce as my 10yr old son can’t eat it. As a result you have to call the restaurant after you’ve placed the order to tell them of any changes.
As I was in a rush I forgot.
When I picked up the food I asked them to take the dish back and swap it for one without sauce.
They said they couldn’t and I would have to order another dish and also pay another £7.50. This was on top of the £83.50 I was spending on food already.
I asked them to ask the manager for discretion and the reply was a no.
I was then asked to take a seat to wait for the dish.
20 minutes later I was given the dish by which time all my order had gone cold.
The whole time I was left sat there surrounded by people eating with 2 big bags of food.
To add insult to injury when I got home my main course was missing.
Awful customer service, poor website and treatment of customers.