For metered service where you pay by the minute (like VoicePulse), see the current discussion
For unmetered where you pay by the channel (like the Spectrum service you have now), I recommend
Some providers offer service where you get ‘unlimited’ incoming on a small number of channels, but pay by the minute for outgoing (calls do not count against incoming channels). IMO Anveo is a good value in this category, provided that you don’t need more than 3 or 4 concurrent incoming calls.