romana

if the number is not set as local in the carrier module, you can just remove the inbound channels from the account, if it is set as local number, just change it to inventory and then remove incoming channels from the account.

If you wanna use wav file format then you can convert the audio to 8000hz as if you are using PCMU then the audio will again get converted to 8000hz, this will decrease the size of your file significantly or if you are open to the option of using mp3, that will also work, both of these reduce the size of your music on hold file. You can audacity to do both.

its simple to do with s3, the modb can be archived and removed periodically while s3 rule can be created to delete the recordings after x time, just look for s3 expiration rule, afaik there is no way to delete a particular recording with api and that is by design.