Lawn gui part C the hardest part

Question

To the Lawn application you created in Exercise 7a, add a
prompt that asks the user whether the customer wants to
pay (1) once, (2) twice, or (3) 20 times per season. If the
user enters 1 for once, the fee for the season is simply the
seasonal total. If the customer requests two payments,
each payment is half the seasonal fee plus a $5 service
charge. If the user requests 20 separate payments, add a
$3 service charge per week. Display the number of payments
the customer must make, each payment amount,
and the total for the season. Save the fi le as Lawn2.cs.

So I am thinking how to do it, do I have to do 3 more " if  "statements that include the number that user type?
or I can just include || and the number in the current "if" statements, but it seems like its not going to work