Siri, the voice controlled intelligent assistant exclusive to the iPhone 4S, has made the iPhone become the hottest smartphone ever, notching solid sales in over 90 countries worldwide.

A new study has shown that 87 percent of iPhone 4S users use at least one Siri feature each month.

Among the Siri features, " Making phone calls and sending text-messages are the most popular," the report suggested. " Roughly a third of 4S owners use Siri to place phone calls, send text messages, or look up information daily or almost daily."

However, many other Siri services, including playing music and scheduling meetings, are getting less attention. "Thirty-two and 35% of 4S users, respectively, said they had never used Siri to perform those actions. Those categories also had some of the lowest percentage of users that did either daily or almost daily."

According to the survey, which was performed by Parks Associates, 55% of iPhone 4S users were satisfied with Siri, whereas 9% were dissatisfied. Others were in between.

The tech giant Apple probably will expand to add more services features to Siri, MacRumors has indicated.