We visited in 2015 and purchased a small, black cell phone, almost like an old Nokia, but smaller. We only wanted to use it for speaking, we don’t want internet on the phone. Do they still sell those? I looked at the Kolbi website and they only have smartphones. We don’t really want that. We used the phones to communicate in Costa Rica and to call home in California. They worked very well, and it was cheap. We left the phones in Costa Rica when we left. We would purchase cards around the country and put in a code to add minutes when necessary. We didn’t purchase the phone at the airport, we bought it in Heredia where we were staying.
I think it would be harder to find a simple one these days, everything is moving towards the smart phone options. It might be better to bring a cheap one down with you. If you search for unlocked GSM cell phones on Amazon, there are a few options (see here). When we first moved down here in 2013, we brought a simple one like you described with us and it worked great. You can buy the chip at the airport and be ready to go.