Lilneenz

Hi all, I’d appreciate some professional opinions on a recently completed kitchen wall tiling job. I hired a tiler who was highly recommended, but due to unforeseen circumstances the actual tiling was carried out by another tiler working on his behalf. I removed the old tiles and had the wall bonded and levelled by my plasterer. Before the job, I asked if the walls should be skimmed and was told skimming would be ideal but that tiling onto bonding would be fine. The day before tiling, the walls were checked and approved. On the day, the tiles went up very quickly. Spacers were used but nothing else. The tiles were due to be grouted the following day and I noticed noticeable lippage and raised this, but was reassured it was normal and would look fine once grouted amd that the walls were to blame. When they left in the daylight the tiles looked ok ish. But now the unevenness is noticeable and very visible under lighting. Is this acceptable ?? What could have caused this ? What should I be saying to the tiler ?