Raj-naah!

Raj and Viraj were very good friends who stayed in the town on Rajapur. Raj was a simple, nice and honest guy who always thought good about others. But he was a bit of a 'traditional' sort of a guy. Viraj was also a very nice guy but was an handicap, in the sense, he was dumb and hence was unable to speak.
When Raj, the slightly 'orthodox' kind of a guy, got married to Rajni, he wanted to change her name to 'Sajni'. For this he needed to go to the name change bureau. He asked Viraj to accompany him and his wife to the bureau. On reaching that place, the clerk at the desk handed a form to Raj and asked him to fill in the names of the husband and wife and the changed names. So Raj wrote his name as it is and wrote Rajni's name to be changed to 'Sajni' and handed the form back to the clerk. But the clerk made a mistake when she also changed Raj's name to Raja in her notebook. Viraj, with his sharp eyesight saw this and started making gestures and actions to imply that the clerk had made a mistake. But the clerk was unable to deciper Viraj's actions. This went on for quite some time during which Raj realised what the problem was and told the clerk about her mistake by singing a song... Which song did he sing?
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He sang: Ishaaron ko agar samajho, 'Raj' ko 'Raj' rehne do!!!