Via your 4HA account, select 'VoIP Services' > 'Account Details', then click 'Advanced' then the 'Options' tab where the 'Music on Hold' setting will allow you to change / upload your default music on hold (as detailed in the screenshot below).  Please note that any uploaded audio files used for this purpose should be in the standard PBX audio format CCIT 8-Bit (8KHz) U-law.



Tip: if you cannot save or translate audio files into audio format CCIT 8-Bit (8KHz) U-law you can call a 4HA voicemail box, record a message, then later save it and then upload it as your music on hold file: voicemail files will automatically be saved in the standard PBX audio format CCIT 8-Bit (8KHz) U-law.