Been there done that got the proverbial. Nowadays my answer tends to be a slight variant when asked this question…

They ask “can you do x” and I say “will get round to it on Monday” (or whatever day you want to use) and then when challeneged the following Tuesday why you didn’t simply answer “I didn’t say which Monday”. Ta daaa. I’ve neverceased to be amazed that these folks never ssk me in the hall again. If you have a junior with you, they need training too … so as you wander away whisper the same magic words to them …!

It’s like training dogs. With some they get it straight away whilst others need to be encouraged to do the right thing.