It is almost expected that a modern call or contact center be able to offer a "call back from Queue" option to your callers.  In fact some call centers are now offering a Call Back with no phone call required from your caller at all!  The caller can text a message to the call center and receive a text back with an approximate wait time until the next agent is ready!   Take the time to develop a custom "smartphone" application and the incoming text message can also contain  business appropriate CRM information like a client ID or policy number. While you are waiting for your contact center to be updated with this advanced SMS text caller option, most modern contact centers can offer a "Call Back From Queue" option. Generally, we want to capture the inbound call, route it to an available agent and if the agent is not available, we will play a customer care message to the caller and keep them in Queue.   Should an agent not become available in the next programmable period of time, we will play yet another customer care message, but this time we might invite them to "press 1" to arrange a call back without losing their place in queue. Should the caller elect to activate this option,  they might then be asked to enter the number that they can be reached at when an agent becomes ready. Optionally you can offer to call the customer back at a scheduled time in the future and also prompt them to enter a date and time for call back.   How this is accomplished is dictated to by the system that you are planing to use for your call center.   Generally, some kind of IVR functionality that can "prompt and collect digits".   The ShoreTel ECC and the CISCO UCCX both enable this option though they do it quite differently. ShoreTel offers a scripting tool that enables calling options through per-programmed routines encapsulated in high level Icons.  These Icons are interconnected on a pallet that graphically mirrors your call flow.   This is "brilliantly simple" and is often all that is required to establish control and options over your call center.   CISCO uses a scripting option based on Java and you will be more comfortable with this option if you have a background in software development.  CISCO is a bit more demanding then the ShoreTel scripting tools, but along with its complexity comes greater flexibility in feature definition.   In the hands of a talented programmer,  you will be able to create features that could not easily be encoded in a higher level graphical scripting tool.   The UCCX Scripts enable you to not only "prompt and collect" but also to "prompt and record"  the callers voice message for playback to the agent prior to placing the out bound return call.