It’s all to do with the DialPlan setting. Mine is set to:
*St4-|1..|0>#t4^0.r8|0>#t40353.r7|0>#t401.r9|0>#t404420..|0>#t4.rd|^0>#t4.r4
but this may not work for you. Basically, it allows numbers starting with 1 to have 3 digits, and assumes international calls start 00. It’s geared towards the UK.
I think the default is:
DialPlan:*St4-|#St4-|911|1>#t8.r9t2-|0>#t811.rat4-|^1t4>#.-
which may work better for you.