Comcast Business Mobile - Online Account Access delegation - How??

Hi all,
I'm running into a frustrating roadblock and hoping someone here has solved it before. We have a Comcast Business account with a Comcast Business Mobile (CBM) sub account. I've successfully added users with delegated access (billing, account management, etc.) to the main Comcast Business account—but their access does NOT carry over to the CBM portal.
I can't find any option in the CBM dashboard to add or manage users separately, and Comcast Business support directed me to call CBM directly. That’s been... less than helpful.  There were no topics that related to my problem in the phone tree menu.   I finally got directed to a live person at CBM, but the call was dropped after a few minutes of silence and call-center background chatter on their end.    I'd love a great number to call to talk to a person who is familiar with this situation, or to know from you all:  Is there a hidden user management setting in CBM I'm missing? Is it even possible to delegate access separately on the CBM side?    Why wouldn't the delegation from the master account carry over?

Any insight or workaround would be greatly appreciated!
Thanks in advance.