Voicemail with one-x mobile/communicator talk path issue

[dcs9150]

HI All,

we have a site with an SBC and an IP500V2 and an applications module running 10.1

we have talk path between and in and out with remote users utilizing one-x mobile and communicator.

voicemail messages and prompts though aren't heard, can see system responding.
initially thought it was a direct media path issue, but after testing different ways no success.

we are wondering if there should be in fact be a port forward to the applications module?

any suggestions would be appreciated.

thanks!