Substation on my property

My father passed away in 2012. He lived on 3 acres. Years ago, probably 25-30 years, he allowed AT&T to install a substation on the right side of his property. I want to say he did a land lease with AT&T but I’m really not sure. This is a flag lot and I inherited it when my father passed away. I received a tax bill and pay it every year. I went through his old files to see if i could find a contract between my father and AT&T. Nothing to be found. Around 2015 I contacted a gentleman at AT&T and he couldn’t help me at all. He said he couldn’t find a contract etc. Knowing my father as I did, he would never sell the property. It’s in my name now and like I said, I pay the taxes and get nothing from it. I’m willing to sell it to AT&T if I could talk to someone in charge but I can’t seem to reach anyone. My next move is to cable off the entrance with my contract info on a sign. That’s about the only thing I know to do. Any help would be greatly appreciated. 

Tommy