Haven't been there in a while. Last week they tried to rip me off again. I told my 2 companions from the place (no take aways) the correct sum before the service came back and - bang - here we went again. About 500 Baht too much. And - again - told them what I really had, the girls confirmed and back came . . . surprise!: the correct bill.
As to Nana and SC. I had girls putting unordered drinks into my cup twice in SC. But I think no big problem there. Never had a problem in Nana so far.