Terrible experience at nandos with they milkshake

Bad milkshake I had bought 4 milkshake from them and it was 200rand Only for it to taste like water and milk, no barone flavor When I had went to the store with the POP They asked where's the pictures to prove that it was TASTED like that and that they cant do anything cause I had no proof of that Yet the waiter that served me also agreed that they didn't make it correct and acknowledged the mistake

And I would like that nandos acknowledge this and try and fix it

We support the business only for them to provide such bad quality