Is it possible to text on iPhone without Wi-Fi through an app?

I remember I had an app called textPlus about a year ago. I used this app to text a friend in the US (from Canada).It used Wi-Fi so it didn't add to texting costs. My friend would receive the messages on their regular phone as regular texts without the app. These apps are very common.

My question is is it possible to text without Wi-Fi on my iPhone? TextPlus used to have an option where if I were to input my phone number and I wasn't connected to Wi-Fi or data, it would receive texts back straight to the iPhone's native texting app. But I believed they have removed it since. Are there any apps like this that anyone might know of?

All of the texting apps that work on iPod touches will also work on iPhones that have Wi-Fi turned off.

I use Google Voice for texting. At home and work, I'm connected to Wi-Fi, so texts go over that connection. When I'm out and about, I'm connected to the cellular network, not Wi-Fi, so texts go over the cellular connection.

I'm not familiar with textPlus's feature set. You should contact the authors of that app about the specific features the app has right now.