High Volume SMS - Question

If the recipient calls the number, the user extension who is assigned with the TF number will receive a voice call if he/she login a RingCentral softphone app or RC app etc. If the recipient reply with a text message, those app will not be able to receive the replied text message but the message is stored in the user A2P message store. You can implement a push notification to receive the reply text message or you can read the A2P message store to read the message.

In addition to @Phong's answer the following reference says:

"Customers can also send text messages to toll-free numbers, so long as those numbers are “text enabled,” and businesses can send texts in response.”

Ref :https://medium.com/ringcentral-developers/power-your-communications-with-toll-free-sms-cf8fdc77bc6e