How can this be possible? Since we do not really differentiate between mobiles and land lines. They are the same areacode and cost the same to call for any other provider that I am aware of. For example to call a US mobile is $1.96 and only $0.05 for a landline.
http://www.freeglobalsim.com/callrates.asp
So, they must have some kind of (very extensive list) that tells them which is which, and they have to build it into how they charge. Have not really testted this since they posted their new rates.
May be someone that knows a little more about how these things work can explain how the rates can be different. The guy (Travis) at freeGlobalsim says he is just going by what rates the carrier they are using told them.
OTOH, it costs only $0.05 and $0.38 to call UK landline and mobile respectively. Similar for all other Western Europe countries. So, if this is true, it's a good card to call back to Europe use for folks visiting the US from Europe.
Phones: Xiaomi Mi Mix 2, Samsung Galaxy A50, ASUS zenfone 3,
Sim cards: AT&T (Contract), 3 UK, Piranha Mobile