dig heels in
dig (one's) heels in
To cling stubbornly to one's beliefs, position, or wishes. Please let me tell my side of the story before you dig your heels in on this, OK? I told Grace she can't go, and now she's dug her heels in as if this party is the most important thing in her life.
dig one's heels in
Fig. to refuse to alter one's course of action or opinions; to be obstinate or determined. The student dug her heels in and refused to obey the instructions. I'm digging in my heels. I'm not going back.