you can try, but it was discontinued almost 16 months ago.. I tried the number once a month for the last 11 of the 16 months that it was reported disconnected.. it is still not working... all you get is silence followed by Beep, Beep, Beep, Beep...
are you sure you didn't call 1-800-Activision for SFC 3?
anyhow.. you have to contact Interplay for SFC OP CD key.. they have a number in their site under Corporate Info, but it is not toll free.