Xfinity came to mark to bury lines in an area that they cannot be buried

Xfinity came to have the ground marked at our home, without our request, to bury our cable line. Unfortunately the area they have marked requires them to dig into the roots of a tree on our property that is over 200 years old and historically protected in our town.  I have tried calling Xfinity for explanation as we didn’t even know this was happeneing and came home to find the flags and spray paint in our yard. But more so, it needs to be done differently to not affect this tree.