You should start and we will help you.
and about your questions:
1- I don't know how can we import this special file type (csv) and use its facilities but in general you can read the file by using FileInputStream class.
2- I think it is better to creat your own data structure containing the attributes first name, last name, phone number and company name and all their types are suitable to be string.
3-In order to sort the data your class should implement compareable interface and override compareTo method and define the style to compare your class instances.
then you can add your data to an array and use the class method
Arrays.sort(yourClassInstanceArray) You just start your job and we will help you.
Good luck