Ackcall not working on cell Agent, SIP agent acknowledge OK


I’ve got this problem for so long, I’ve tried everything and I am out of ideas, please help.
I have BroadVoice and agents logged in on SIP phones and cell phones over broadvoice.

I need them to acknowledge by pressing # to avoid transfer to cell VoiceMail,
ackcall works totally fine on SIP phones but # is ignored on cell phone.

What to do to make it working?

Please help, any suggestion would be higly appreciated.

Thanks in advance,