A customer is charged for using various data services on the mobile network.$$ When a call is made, the signal is sent to the tower.$$ The tower has a switch in which the files are stored.$$ Each call which is made is stored in the form of a record in the file.$$ The record consists of information such as$$

From which number the call was made$$

To which number$$

Call duration$$

Pulse rate$$

The file consists of a header which will give the number of records present.$$ There are different types of calls like STD$,$ ISD, and LOCAL for which the pulse rates are different.$$ Draw the use$-$case diagram and sequence diagram.