Here you go:
Custom Size - Either you select custom size when confirming paper size, or you do it through this guide to set it as default.
And when it comes to the dial tone:
Login as the System Administrator
Outgoing fax volume:
Press Machine Status -> Tools -> Service Settings -> Transmission Defaults -> Audio line monitor.
Incoming fax volume:
Press Machine Status -> Tools -> Service Settings -> Embedded Fax Settings -> Incoming Fax Defaults -> Ring Volume.
Hope this helps.