Words of advice for cell phone users

I have a company supplied phone with AT&T service. The company I work for has locations in both the US & Canada, so our phone service is covered "in part" in both Countries. However, when I am vacationing in the UP of MI near the Canadian border, my company will give me temporary International sevice to avoid the roaming fees, which is mostly ok....but when they do that they also remove my ability to use my phone as a personal hotspot. I never got a clear answer as to why from my IT people.