Yes, it's possible, although it's not recommended because the service you can provide to your clients will be much better once the agent is connected to both channels.
For example, the agent has a "shared brain" across both phone and SMS, and can deliver a higher level of service with all the capabilities built into both channels, which leads to more appointments, less drop-off, and zero conversations falling through the cracks.
That said, if you only need an agent on one channel, you can
reach out to me and I'll provide specific pricing.