How do I design an address book (hashing based searching supported) ?

I want my address book to record and store all data in a CSV file (initialized from a CSV file). Each record should have the basic fields included to collect data such as : user name, phone number, mobile phone number, address, memo.

I want it to use (mobile) phone number and user name item respectively as the keywords and build the

index with hashing

I want this to support searching with the user name and phone number/mobile phone number.

Lastly how do find a solution to avoid collision. Thanks.