Tried putting *99, *98, *97, *96, and a bunch others in front of the number - no change.
Changed my outbound caller ID to a second number I added to the account - no change.
Added my number to the contacts - no change.
Disabled / Enabled 10 digit dialing a couple times - no change.
Tried +1, no +1 - no change.
Tried ooma support - "it's been escalated"... how long should I give them before giving up and returning the equipment for a refund, since it isn't doing the one thing I need it to do more than anything else?
If the cell phone is a local call, with either the same or nearby area code ("NPA") or overlay, then it's possible that 7-digit dialing (or 1+7-digit dialing) could work. But that depends on the specific areas codes and exchange codes between the two numbers.
The *96, *98, and *99 codes only affect call clarity, not connectivity. Changing the outbound caller ID to a second number shouldn't matter, unless the cell phone was blocking the first number for some reason. And adding numbers to the Contacts list only affects whether Ooma blocks incoming calls.