If I keep my data on but also use Wi-Fi will it use my data?

I just got an iPhone from us cellular. I use Wi-Fi to save data, but I can't receive group messages if my data isn't on. If I keep my data on all the time, but use Wi-Fi, will it use my data? And if I keep both on will it use my Wi-Fi instead of data?

It actually depends on your phones settings, you can limit certain applications to Wi-Fi only and other to both

So try to find the settings on your phone