DATA USAGE

I just left AT&T to come over to Cox.  With AT&T I had unlimited data - but bill was about 175 a month which included cable and phone.  Now with Cox 3 weeks - not working from home and it get a text today saying i have used 78% of my data.  I go online and it says last time my phone and iPad were connected was Jan 29th.  How in the heck can this happen????  My son plays games but still.

Should I go back to AT&T?  At least I didn't have to worry about data or what my bill was going to run.