There are plenty of synonyms for the phrase "gets off someone's case". One of the infallible options is to "lay off," meaning to stop badgering or nagging someone. Another possible synonym is to "back off," which conveys a similar message of leaving someone alone or giving them space. "Ease up" is another choice, implying that the other person is being too hard and should be more lenient. "Stop hounding me" can also be used interchangeably, signifying that you want the person to stop pestering you. Other options include "stop bothering me," "get off my back," and "let it go." All of these phrases express a desire for the other person to cease their annoying behavior.