Update voice-testing.mdx

Author: yoshita53

fern/test/voice-testing.mdx

@@ -117,4 +117,10 @@ Begin the call by stating your need for an appointment, specifying a preferred d
 1. The voice agent confirms the requested appointment time clearly and accurately.
 2. The agent reiterates the appointment details to ensure clarity.
 3. The scheduling process ends with a definitive confirmation message of the booked appointment.
-```
+```
+### Frequently Asked Questions
+
+<AccordionGroup>
+    <Accordion title="Is testing free?" icon="phone" iconType="regular">
+        No. Test calls cost you half of regular calls.
+    </Accordion>