Vivid Wireless 3rd Party VoIP Options

I've ordered a Vivid Wireless modem and while i'm waiting for it to arrive i'm trying to figure out my VOIP options. I emailed vivid wireless and this was their response:

If the VOIP is a 3rd party service that doesn't require settings being changed through the modem you can use it on our system.

I'm not exactly sure what this mean and was hoping someone could clarify or point me in the direction of some suitable VOIP service providers. Ideally i'm hoping i'd be able to keep my landline number and use the phone to call local,national and international.

Thanks