Why don't I receive messages unless my cellular data is on?

I got this iPhone 3 months ago. It's the 5th one. This constant problem is that sometimes I don't get messages unless my Cellular data is turned on. I need to fix this cause its really annoying. Like for example 10 ppl texted me on Christmas Day saying merry Christmas. On January 4 I turned on cellular data while in my car & then I got them all! And it's crazy because It had the date of Christmas & the exact time.

Uh… Because SMS text messages *travel only on the cellular network*.

SMS message service is provided by your carrier. SMS messages are encoded data that are sent along the same network used by voice calls. They do NOT travel on data networks, so if you don't have the cellular network turned on, you will receive no calls and no texts.

Only data-based texting apps use the data network (whatsapp, iMessage, etc).