Hello fellow DU business folks. I've been working with a company recently and I wanted to share what they do with the community because business telephone systems have evolved dramatically over the past decade, and it's now possible to get amazing functionality from virtually free components, most of which are open source. BandTel, from my old stomping grounds of Laconia NH (and LA, but the real dudes are in Laconia), is a world leader in providing
SIP Trunking and Asterisk PBX services to businesses of all sizes. If you have to have phone numbers, especially 800 numbers, that need to work from other countries, and you don't want to pay a crazy fortune, they're your guys. Asterisk PBX is an open source PBX which gives you functionality that previously was VERY expensive. Plain Old Telephone Service has been bypassed by Voice over Internet Protocol (VoIP) phones because of the vast differences in cost.
Check BandTel out if you have expensive phone systems and are looking for alternatives. There are other companies as well that compete with them, like Bandwidth.com, so shop around and get the best deal, but I like them personally so I give them my recommendation.