The only way the Auto Attendant can be reached is through an {aa} type rule in an InboundCallRoute.
If you're calling OBi-to-OBi (**9xxxxxxxxx), then you're using the OBiTALK Service and there has to be an {aa} type rule there for calls to end up at the Auto Attendant.
If you're accessing the OBi directly, did you remember to disable Auto Provisioning? If not, the OBiTALK Web Portal will overwrite your changes with its settings.