All contacts can write you a reply to the 2WAY sender.
You can see replies from your subscribers in 2 places:
1. In the Contacts Book. Contacts that have sent you messages will get a corresponding icon. By clicking it you can view the messages the contact has sent to you.
You can filter the contacts that have sent you incoming messages.
2. In the Detailed Report on 2WAY SMS, you can view SMS messages of all types.
You can filter incoming SMS messages using a Filter.