at one's disposal
Call to come, wave to go, call: wave. Wave: wave. I'll come as soon as I move, and I'll go as soon as I swing. I'm very obedient.
source
Chapter 6, section 5 of Lao She's Autobiography: "it's not polite to call on unimportant people and wave them away."
Examples
We promise to come as soon as we are called, to go as soon as we wave, and to obey the command absolutely.
at one's disposal
be somewhat refined in one 's rough way - cū zhōng yǒu xì
be helpless and in the greatest straits - jì qióng lì jí