I needed a plasterer and my builder said I'll do one wall as a sample free of charge and if you like it I'll do the whole house with a good price.
The sample was amazing, great quality, smooth finish, brilliant; I was impressed and said yeah let's go ahead.
After few days I realized the quality has degraded and the surfaces are becoming more bumpy and rubbish.
Basically what he had done was to do the initial sample with a good plasterer then some of the remaining walls with another junior plasterer and paying him peanuts to save money!
I complained and said you're cheating and I didn't agree with such rubbish quality and only the quality of the initial sample so I won't pay you for this. Do not bring your junior plasterer again because it'll cost you more as you'll have to redo it.
... after some time and naggings, he agreed.