Expanding on bluechip's post, there are several free tollfree service providers that don't require you to setup an account.
tf.callwithus.com is one of these providers. I used
tf.callwithus.com for years and was very happy with their service, but recently made an 844 call that failed.
tf.callwithus.com didn't think it was a tollfree number. I don't know if they can't handle all 844 numbers or that particular one. I have since switched to
tf.arctele.com.
I think (not 100% sure) localphone requires you to setup an account to use their service. I'm not familiar with Anveo or Phonepower.
Circle.net is another cheap service provider that doesn't charge for tollfree numbers.
Do you currently own an OBi?
Do you have an account with a service provider?
If you don't have a service provider I would setup Arctele on SP2, otherwise you would have to setup a dummy SP to use a Voice Gateway. This will leave SP1 for your main service provider.
Post back what you want to do and I or someone else will walk you thru the setup.