Waitress argues with patrons/ NO CUSTOMER SERVICE

Bad service! I am so disgusted with the service received. Ordered the specials and the waiter starting raising her voice and arguing about the special called her colleague which came with a massive attitude and who also could not justify why we could not share buy one get one free special. She went off to an extent that a by-standing guy came up to her and said he could do this the night before. I asked why would the rules and T&Cs which was not stipulated on the specials menu over. I would fully understand the logic behind it if we were having 1 drink but this was not the case and loosing 2 tables of clients unhappily as we moved next door to the next restaurant and received very pleasing service. Which I then understood why the place next door was packed and dockside did not have 1 client. Never have I experienced staff who doesn’t have any customer services to this extent