I'm not 100% sure, but I think RAS is for accessing remote computers.
In order to dial a number, TAPI (telephony API) would be the right choice.
However, this has no managed equivalent either.
But, if you know your clients will always use analog modems connected to a
serial port, you could of course use one of the serial port classes
available on the net, and send AT commands directly.
Google for "AT commands", and try them with some terminal program (like
hyperterminal).
Niki