You could try this if you purchase an Ooma Linx device for faxing or having separate accounts for each Premier phone number. You can isolate the second number, from your main number, by creating a private account.
(It also creates a separate e-mail account for the second number).
Private Account Setup. Must have Ooma Premier Service:
Go to My Ooma https://my.ooma.com/phone_numbers
, and after the page opens click on "Add Private Account". A window opens that has blanks to fill in. Give the account a name and fill in the blanks, then click on the Save button.
In the Private account that was just created, click on Set Up device and fill in the blanks for the Telo handset, or new HD2 handset or new Linx device. (Cannot mix Telo HD1 handset(s) with HD2 handset/Linx devices, but can have up to four Telo HD1 handsets, or a combination of up to, but no more than a total of four HD2 handset(s) and/or Linx device(s). Linx device ID can be found on outside Linx label. HD2 handset device Id can be found by clicking on HD2 handset Menu button, then using the Navigation Pad bar, select “About handset” (circle i Icon). Then press the Select button which is located in the middle of the Navigation Pad. Device ID number/letter combination is in the window list that opens.
In the Main account, click on the phone number that you want to use in the private account. In the window that opens called "Managing Phone Numbers", move the number to the Private account, by clicking on the down arrow, selecting the Private account and clicking on Save. Or for $5 a month, in the Private account you can click on the "Add New Phone Number", follow the links and follow instructions to add a third phone number. This option is used mostly for Fax lines. (Remember that only two calls can be active at one time, even if you have three or more lines, using an Ooma Telo).
If you are using an Ooma Linx device, in the pull down menu following Mode the following can be selected: Phone, Fax machine, or Alarm system modes.
It will tell you that it takes five minutes for the Ooma servers to recognize this transaction, but I found it take almost an hour to it work properly. Then test making/receiving phone calls, or faxing.