Thank you for your suggestion. I do use T-Mobile and pay extra for their international system. The problem I have using my US cell in Argentina is that to make free whatsapp calls my phone needs to show the words T-Mobile at the top left of the screen next to the wifi sign. If it does not show that, you can still make calls using Whatsapp but you pay $0.20 per minute rather than free. I am often connected to a wifi, and still the T Mobile words do not appear on my phone, so I end up paying for the calls. Because I need to make lots of calls, I end up with a huge bill from T-MObile, even at $0.20 per minute. That's one reason why I thought that using a pocket wifi may solve my problem, but I am not sure if I can rent one in Argentina and what the cost would be. I'll find out soon. I appreciate your response and suggestion. See you soon.