Need information on what Xfinity is planning with my backyard

Xfinity is putting new lines in my neighborhood in Aiken,  SC. They put a general notice on people's doors a while back. They marked the area of my front yard that is close to the road,  where there is an easement.  That was done over a week ago it's fine,  they're allowed to dig by the side if the road.  But i found yellow lines spray painted in my backyard today.  They came when i wasn't home.  I wasn't aware they have a right to dig in my backyard,  which is far from the road. Also i have no idea when they will do this.  I don't know who to call,  because when i try to call customer service or use the chat feature i get asked for my account information.  I don't use Xfinity. I don't feel comfortable asking the work crews in the neighborhood because i get really hard glares when i drive by them. If i can't get an answer tonight,  I'll be calling the city engineer in the morning.