I have had the same issue and called customer support 3 days in a row. Each day they assure me it is all fixed.
But it is not. My preferences are set to only roll over to my cell phone in case of an outage. However, even if I am not on my Ooma phone, it is ringing a few times and rolling to the cell phone. Then it cuts out and sometimes the caller calls back.
In addition, since their call center is in the Philippines, it is hard to understand some of their English.
So I would not recommend Ooma. Maybe Vonage is better.
Review about: Ooma Premier Home Phone.
Reason of review: Poor customer service.
Preferred solution: Let the company propose a solution.