Poor customer service and explanations provided to the customer are unreasonable and not logical

I ordered my meal using the APP and specifying and selected the specific piece of chicken which I wished to receive from Nandos, when the incorrect piece of chicken was provided to me which I understand is the stores issue and not necessary a fault on MrD, the response I received was extremely poor and speaks to the lack of customer service. The initial response which I received from MrD was pathetic, firstly telephonically they advised that I would receive a full refund after I send them a picture, which I promptly did. The next day they advised me that they cannot control if a store does not have availability of a specific product, however I am fully aware of their protocols, that if a customer wants a specific product and the store does not have it then the order will be cancelled on their side due to non- availability of the particular product. Previously I ordered on the app and the store did not have the product, then my order was cancelled on MrD due to unavailability of that product. Therefore the explanation provided to me by the MrD's representative is totally invalid, unreasonable and the explanation provided is totally unwarranted. You need to provide your customer with valid and reasonable explanations if you do not want to refund them. Because stating that Nandos did not have a breast portion of chicken is total nonsense and if there was no availability then MrD should have cancelled my order as they do in that situation and as per their normal protocol and procedure when a product is availability. This is extremely bad customer service where you cannot firstly provide the customer with a reasonable explanation as to why the refund cannot be granted and also secondly initially as me to send pictures and advise that I will be refunded only for me not to be refunded so why waste my time in taking pictures etc. This organization needs to seriously work on their customer service and provide logical explanations to customers if they wish to disappoint their customers.