When we have MP3 enabled we want ALL voicemails to be MP3 EXCEPT the ones that need to be transcribed, which will be WAV.
When transcribe_enabled is set to true, ALL voicemails currently become WAV even when MP3 is set.
This change ensures that ALL voicemails remain MP3 except the extensions that have voicemail_transcription_enabled set to true.
Note: The reason this was not working is because setting transcribe_enabled to true also sets voicemail_transcription_enabled to false for ALL extensions BUT it is not written into the database. Therefore a SAVE is required for ALL voicemails to ensure this field is written to the database. Changing to ~=true gets around this problem.