In "The Sunday Philosophy Club" by Alexander McCall Smith, Isabel recognizes a specific etiquette regarding phone calls. She believes that calls received before eight in the morning should be treated as emergencies, indicating a respect for personal time and boundaries. Calls made between eight and nine, however, are seen as intrusive, suggesting a delicate balance between social obligations and personal space.

Furthermore, Isabel notes that calls are generally acceptable until ten in the evening. Yet, she emphasizes a need for politeness after 9:30 PM, where one should apologize for any disturbance caused by their call. This establishes a clear understanding of acceptable communication hours, reflecting Isabel's awareness of social norms and the importance of consideration in interactions.