While incoming calls cannot be fully turned off, contacts can be notified that a line is only used for texting. This can be accomplished by providing this information in the greeting or voicemail recording. More on voicemails here.
All incoming calls can also receive a text message from your number once the call is hung up. This auto-response can be configured in Settings > Auto Responses > Auto-Reply to Incoming Phone Calls. Learn more about auto responses here.
Alternatively, you can have all calls that come into your Avochato number forwarded to a business or personal line. Learn more about call forwarding here.