dig one's heels in 顽固不化，坚持己见，越发固执，不愿妥协，固执己见

【例句】
People are like this, when you tell them no. They will dig in their heels.
很多人就是这样，当你告诉他们不行的时候，他们会更加的固执己见。

No matter what anyone says, he always digs his heels in and refuses to compromise.
无论别人说什么，他总是坚定不移，拒绝妥协。