You need a WiFI connection and download an app that allows free texting such as Google Voice. Google, there’s lots out there.
Speaking of cellphones . . . What is the rock-bottom cheapest option for someone who rarely uses her phone, needing it only for emergencies and a rare drive out of town? I’ve heard Walmart offers “burner” phones very cheap. Can you get one and buy an hour or two of minutes that won’t expire?