The recording may be heard at timecode 2:28:00 of the video at this link:
https://www.youtube.com/watch?v=HXfkdZ4BBr0
The conversation, allegedly between Mahlangu and Kgomo, takes place in isiXhosa.
The link is to the SABC’s recording of State Capture Inquiry - Robert McBride, 15 April 2019 Part 2 on Youtube