Substation Box on property

Hello! My husband and I bought a home with a “substation” located on our property. We are wanting to know what this box actually does. Also, we would like to have AT&T internet service but we were told that we aren’t in the service area? If so, what does this box actually do? We would appreciate to talk to someone who can give us factual information. We would like to become customers but don’t appreciate the run around considering we inherited this equipment on our property. 

Thank you