Grasshopper on International Sim Cards [closed]

Will IP Phone Software Services such as Grasshopper or the like, function with an international Sim Card and no phone number (except the international Number)?

We jump from country to country regularly and require 24/7 cell + sms access on a local (to the USA) phone number. We struggled to find a carrier that supported the countries we're traveling to. So, we've been using local sim cards (local to the country we're in) with no phone access on the card while attempting to utilize a soft phone / ip phone software service unsuccessfully.

I've been struggling to find a solution to this. We tried grasshopper and ported our 3 USA phone numbers to it. However, once the ports completed, nothing seems to work except outgoing calls. I'm not sure anyone at Grasshopper understands fully what we're trying to accomplish (to have working USA numbers, fully accessible while we travel to any random country).

I'd switch / port our numbers to another similar carrier if needed. I'm not sure if I'm just wasting my time and this kind of setup will never work? Do these sort of services require a sim card present with a local carrier to process the SMS / Phone calls thru somehow? Or, am I just having bad luck with Grasshopper and this should work?