It was an altogether different age, when having a telephone at home was a status symbol. And the waiting list for a new phone connection was sometimes years long. It was also the time when there was no pulse for local calls (at least in Shillong), it didn’t matter how long the call was, you would be charged for only one call (80 paise, if I remember right was the unit charge during my school days). Then things changed with the advent of Internet through dial-up connections. A light lit above some babu’s head in the Department of Telecommunications and the pulse was changed to three minutes.
The advertisement below is from even an earlier era, when telephones fell under the purview of the the Posts and Telegraphs Department (P&T), which was, in January 1985, split into two different departments, Department of Posts and Department of Telecommunications. MTNL happened a little later and BSNL to a decade and a half. In P&T times, telephone connections were few and far between and without exposure to telephones most Indians didn’t know how to use one (the rotary dial flummoxed me as a kid) This necessitated that the department release instructional ads on how to best use the device.
Didn’t happen to notice similar ads when mobile phones first made an appearance.