There are system extensions and then phone extensions. The system extensions are the ones used for 3cx fax, IVR, etc.
You should make and use an IVR recording to do your initial greeting and include a key that points to another IVR for your directions. Within the direction IVR you could say hit 9 to repeat in which case the same direction IVR will replay (gives people like me a chance to ensure I have the directions down correctly) and then another key (and maybe the timeout) that will allow me to go back to your initial greeting IVR and start again so that I can make new selection. heck, you could even have another set of IVRs to provide directions based upon a compass heading ( if coming from the north, press 1, if from the south - press2, etc.) or even if you have major well known landmarks.
If you select a phone extension (csr in your case), then you are correct. It may be problematic to go back, but this depends upon how you have the forwarding rules set. If you get into Vmail, then you cannot escape (back) to the IVR that sent you there, but you can hit a key to get to the operator.
Keep in mind that the IVR is there to direct or provide info to routine, repetive requests. It is meant to alleviate some of the workload from the folks who would otherwise have to handle. Directing to a phone extension implies a conscious decision that someone on the other end will will answer and help. You could change the rules such that if the phone extension is busy or unregistered, it could go back, but this also implies that the Vmail for the extension should be disabled.
Play some more with the IVR feature. It can be a really good tool.
If an IVR is not good for you, look into queues.