Hello,
My name is Zied, I am a computer engineer from Tunisia (UTC + 1).
I have more than 6 years of experience with Twilio API.
I have done something similar to your requirement before, the caller can request to be linked to an agent, or he can request a callback. As soon as an agent is available, the client will be automatically called and connected to the agent.
Thank you for taking the time to review my application.