How to capture multiple responses from a user in a n8n workflow using Meta's WhatsApp API?

Question

I'm new to n8n and I'm facing an issue while capturing multiple responses from a user in a workflow.

Context: I have a workflow where:

1. A user sends a message via WhatsApp.
2. A webhook (POST) receives the message.
3. A code node filters out unnecessary data.
4. A switch node makes a decision based on the option selected by the user (e.g. "a", "b", "c", "d").
5. WhatsApp sends a message with sub-options (e.g. "a1", "a2", "a3").

Issue: Although the flow works fine for the first response, I'm not able to capture the second response from the user. The initial webhook receives the first message, but I don't know how to handle subsequent responses.

What I've tried:

1. Using a second webhook to get additional responses (didn't work).
2. Trying with HTTPS in the Facebook Developer Meta API for WhatsApp, but only found push methods.
3. Trying to sequence two webhooks, but Meta Developer only allows binding to a single webhook node.

Sample JSON code:

[
{
"messaging_product": "whatsapp",
"contacts": [
{
"input": "",
"wa_id": ""
}
],
"messages": [
{
"id": "wamid.HBgNNTQ5MTE2NDU1ODczNhUCABEYEjZFRTIzNzc0MDQ0NTVEOTE3NwA="
}
]
}
]

Question: How can I capture the second user response in n8n using the Meta WhatsApp API?