If you have Bixby text call set up then you can select this whenever you get an incoming call. Bixby will answer saying that it's talking on your behalf and ask their reason for calling. You can then choose from the options of quick responses available or you can type with the keyboard. Bixby will then read out the response to the caller. You can read through the conversations as well.
Bixby text call is available on these phones:
If you have any of these phones, you can set up Bixby text call.
You'll see the Bixby text call on incoming calls, and you can tap on it to use the feature. A new screen will appear where you have to swipe up on the green coloured icon to initiate Bixby text call. As mentioned above, Bixby will inform the caller that you're using an automated voice, and ask the caller who they are and also why they're calling.
Once the conversation begins you'll see it transcribed on the screen. You can choose a quick response or write your own. You can also choose to stop using Bixby and switch to a normal call by tapping on the voice call option on top of the screen.