MMS while international roaming

I was in South America a couple of years back and I had free internet service through T-Mobile; however, messages and talk were available but very expensive. Easiest solution was to get the WhatsApp application and I could send messages and also voice and video through the internet at no cost. Most everybody in South America uses WhatsApp so it is very convenient. I use WhatsApp in the States for all my international calls at no cost.