Hello
You're saying your data is being used on your Unite hot spot device, right? And with your work laptop? I don't think your phone is causing troubles here, more likely it is your computer that's using all that data, however it's virtually impossible for us to know how your data is being used, AT&T only keeps track of the total amount. Do you watch any videos online? do you download large files or attachments? any web conferences or anything else that could be using all that data?
Thanks,
Dmitriy