I'm helping an elderly friend sort out her phone & internet. She has just got Skinny Jump for $5/m and would like to use Kiwi VOIP (recommended by her daughter who uses them).

I noticed her Skinny 4G modem (a Huawei B315s-608) appears to have a built-in ATA as it has a phone jack on the back.

Skinny seem intent on telling everyone you can't do VOIP on their service. My research here on gz tells me their 4g internet uses CG NAT, but it's unclear if that's a deal-breaker for VOIP. I can say my own VOIP account (using 2Talk) via an app on my Mac seemed to work fine using her Skinny Jump broadband.

So my question is, can anyone confirm that a VOIP service (in this case Kiwi VOIP) will work on the Skinny Jump 4g broadband, and if so whether I will be able to configure her Huawei B315s-608 for VOIP?

If not, would it be possible to configure a spare Huawei GH659 that I have (Vodafone firmware) to provide the VOIP for her? When the GH659 is plugged into the B315s I guess that would be double-NAT, but would it matter?

Ideally I wanted to get her set up with unlimited national calls — apparently she talks for hours almost every day lol. I tried to convince her to use her mobile for this but it's not going to happen... at 79 some things just aren't easy to change :) Unfortunately I'm not finding any way to get that at reasonable cost from a landline without a broadband bundle (which she doesn't need).

Grateful for any advice :)