Mammoth IFR Clearance Frequency...

Hi Folks,
New guy question...I tried the published (125.75) frequency for Oakland Center for an IFR release from Mammoth (KMMH), but no luck. Is there a Pilotedge trick here I should know about?
Thanks!
-D
New guy question...I tried the published (125.75) frequency for Oakland Center for an IFR release from Mammoth (KMMH), but no luck. Is there a Pilotedge trick here I should know about?
Thanks!
-D