and another VoIP service provider - SIPZoo. This one is offering a free trial and you can use any SIP device with their service - which is a knock against many competitors - who also often lock their SIP-capable devices. Also, as far as I can tell there is no credit card needed for the free trial. I'd assume this trial is temporary otherwise people could keep signing up with fake names to get the free trial. That's one easy way to bankrupt themselves.
They also offer a cheap "teaser" plan of $9/month, but it only includes 2500 U.S./Canada minutes. Their unlimited plans start at $29.95/month.