If you are a business in which uninterrupted phone service is of critical importance, I would be worried. However, since I am self-employed one-person research contractor, whose office phone is his cell-phone, I am not worried. Do whatever makes sense points wise. The other long distance companies will be more than happy to take your business whenever you want them to, and the changeover should take less than a week, which would surely be enough time to get off of a sinking ship. UNLESS, like I said above, you are a business whose phone lines are of critical importance, e.g., a call center.