Sándwich Barón Bryanston - bad food and service

I received a sub standard sandwich from Sandwich Baron Bryanston on Thursday. The sandwich was a chicken mayo crispy chicken, when I started eating , it was dry. When I opened it there was no mayo. I then contacted the owner of the shop and he was disinterested and rude. I never wanted to write a review just let the owner know. But after the response I received from him I have no option. For bringing this to his attention, he called me a Karen, which I do not appreciate. Clearly the owner has no use for customer service and is arrogant. I have photo’s of the sandwich and my chat with the owner, to show the sun standard sandwich and really poor service.