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In that case, then it's up to Skype and probably your carrier. Just like FaceTime over cellular is apparently left up to the carrier.
 
I just learned a new feature

I use Skype for landlines and from skype and skype but until this weekend thought I had to be on a wifi to use it.

:D Happy Camper!!

I should have added that I'm in Canada. My IP4 still requires wifi for skype
 
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