The narrator introduced himself to Anil as Hari Singh. He changed his name every month to escape arrest. Hari Singh wanted to work for Anil but Anil had no money to pay him regularly. ... He also taught Hari Singh to write his name and promised to teach him to write whole sentences and to add numbers.

The narrator of the story changes his name every month due to his job as a spy. The details of this are explained below.

Job as a Spy
The narrator works as a spy for the government. His job is to gather information on various people and organizations. In order to do this effectively, he needs to keep his identity hidden. If his true identity were to become known, he would be in danger, and his work would be compromised.

Changing Names
To keep his identity hidden, the narrator changes his name every month. This way, if anyone were to try to track him down, they would not be able to find him. Each new name is carefully chosen to fit the personality and background of the person he is pretending to be.

Cover Stories
In addition to changing his name, the narrator also creates cover stories for each new identity. These cover stories are designed to explain why he is in a particular place, and what he is doing there. For example, if he is pretending to be a businessman, his cover story might be that he is in town to meet with potential clients.

Importance of Secrecy
The narrator takes great care to keep his true identity hidden. He is aware that his work is dangerous, and that his life is at risk. Therefore, he is always on guard, and he never reveals too much about himself to anyone.

Conclusion
In conclusion, the narrator changes his name every month because he works as a spy, and he needs to keep his identity hidden in order to do his job effectively. By changing his name and creating cover stories, he is able to move around freely, without raising suspicion. His work is dangerous, and he takes great care to keep himself safe.