How do I correctly implement this switch statement to compose a string?

I want to produce a string that is a single letter (A, B or C), followed by two random numbers. I have written the following code:

enum typeOfPerson {CHILD, ELDER, BOOMER};


    public String setNumber(Report.ReportType type) {

        Random rand = new Random();

        String number = String.valueOf(rand.nextInt(10)) + String.valueOf((rand.nextInt(10)));
               
              
        switch (type) {
            case CHILD:
                String prefix = "A";
                break;
            case ELDER:
                prefix = "B";
                break;
            case BOOMER:
                prefix = "C";
                break;
    

                 accountNumber = prefix + number;

        }
        return accountNumber;
    }

When I run the code I just get the two random numbers, without the prefix. I am unclear where the error is, but I am guessing I did something wrong with the switch statement.