Texting/messaging apps are free, and telephone is built in, along with so, so much more. I was a long time businessman, too. These days potential business comes via the published messaging address. Check it out gringohombre. WhatsApp is widely used all over the world, that's a good one to study. But there are others, like Messenger (built into Facebook), Line (very popular in Asia), and lately Signal (which touts very high security). The horse was once a "tried and true" way to travel!