Hi
Run a debug q931 on your router, and get it logged out to syslog.
When you get a report of a non-prefixed call, search the syslog for the calling number.
Check whether the SP is sending in the 'national' number type that triggers the prefix.
It may not be doing this consistently; or you may need to configure the other service parameters (international, unknown) appropriately.
Regards
Aaron
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Aaron
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