BETA
You can enable 2-way SMS on a hosted voice tenant by enabling the Service in Atomic. Navigate to the Hosted Voice Service in Atomic and go to the Manage page. On the Hosted Voice tab, you can toggle the 2-way SMS to ON.

Once the feature has been turned ON, you will then need to select an active SMS service that has been assigned to the same customer. This essentially means that all outgoing SMS from the Hosted Voice account will use the selected SMS service.

When a SMS enabled number has been assigned to the relevant Hosted Voice account, administrators of the PBX will then be able to assign the number to the appropriate user / extension.
Requirements
To enable 2-way SMS, you will need to ensure that a few items are activated and enabled to ensure smooth operation of the service.
SMS Service
Ensure that you have an SMS Service created and is assigned to the same Hosted Voice customer.
Virtual Mobile Number
To run a 2-way SMS service, you will need to have an SMS enabled number, like a Virtual Mobile Number (VMN). You will need to ensure that the VMN is assigned to the Hosted Voice account. This is to ensure that both incoming calls and messages are delivered to the correct place.