I too have switched to a virtual fax number for my Hamiltons. Rather than paying for an actual fax line, I now pay $10 a month and save on paper and more importantly ink. I first tried Ringcentral.com, but for some reason my ACW's would not connect successfully to the service. I would get faxes from other people but not my ACW's? I now use MyFax.com for $10 per month with great results.
I highly recommend switching to one of these services but I would suggest you thoroughly look into the pricing and test the service before committing. Most services will let you try it for 30 days at no cost. Each service has a similar, but different interface, some which you may not find convenient to use. You may also find, for whatever reason, your machine works better with one service over another. Pricing seemed to vary quite a bit as well. I have six ACW's reporting each night plus at least one monthly report for each machine a month, that's at least 200 faxes per month. My service has never cost me more than $10/mo, but some others will charge you per fax once you exceed a set number or some even charge you to store the faxes over a set amount of days. If I remember correctly, eFax seemed to be one of the pricey services.