Making Use of Wideband Voice Right Now!: OnSIP
You will find references to Junction Networks’ OnSIP hosted IP-PBX service scattered all over this site. I’ve use them since the summer of 2007 for my home office phones. They’re extremely reliable, 100% SIP based and even wideband capable in many respects.
The basics of the OnSIP service are pretty simple. If you are a company and need the usual services you establish an OnSIP account, selecting one of their monthly service bundles. These run from $39.95/mo to $199.95/mo, scaling up to suit companies of various sizes. They offer a 30 day free trial to let you get your feet wet.