This is the most serious kind of booking fault, and it is fixed. When the assistant had read out times for one day and the caller asked for a different day at the same time — “can I do Thursday the thirteenth at ten o’clock?” after being offered Wednesday — it confirmed the day it had offered, not the day the caller asked for. Rephrasing did not help: the same wrong day came back each time, including when the assistant asked which of the two days was meant and the caller answered.
Nothing was ever written into a diary wrongly — the flow stops for confirmation before anything is recorded. The harm was that the caller was told the wrong day and could ring off believing it, and that asking again in different words did not help.
A day the assistant did not offer is now treated as a request, not a choice. It looks that day up properly and either offers the real times on it or explains why it cannot. Naming one of the days it did offer still works exactly as before.
Three more ways of choosing a time now work. “The thirteenth at ten” understands the date. A bare number — “eleven please”, “ten”, “nine” — picks that appointment, which is how most people answer when three times are read out to them, and it previously selected nothing at all. And “I’ll take the earliest” now books the first one offered. Where a business offers two appointments at the same clock time in different halves of the day, a bare number is never guessed at — the assistant asks.