We need help with writing a Twilio (Run Function)

We have IVRs built in Twilio and we would like to enhance it by coding a function to alter the greeting from a custom app. We don't need help with App itself but we need help with writing a function on the Twilio side. The purpose of the function would be to inject an API call to a studio script to alter the active greeting to a closed greeting and toggle it back when the holidays are over. The process would be to write a Twilio function, insert it under the studio script and invoke it with an API request. Please apply for the project only if you have handled such requirements before.