As the title of this post states, as a Sell user, there is currently no self-service option to upload a personal voicemail recording to Zendesk Sell. Instead, you have to contact Zendesk customer service, provide them with the recording, and wait for them to upload it to your account.
Also, you can't delete personal voicemail recordings from your account. Again, you need to contact Zendesk customer service and tell them which voicemail recordings you want to be removed.
In each of these situations, it'd be a much better user experience to upload and remove voicemail recordings on our own and not rely on a few Sell engineers at Zendesk to do this on our behalf.