IF then Else code in my SSRS report not working

below is my code for identifying format of the amount.

if chargeNum is not equal to invoiceNumber, then set currency to "C" else currency to "N"

then i'll set the chargeNum to be equal to the invoiceNumber before returning the currency

my code below is not working. What am I missing?

Thank you !

Public Shared invoiceNumber as integer
Public Shared currency as string
Public chargeNum As Integer=0
Public subNum As Integer=0
Public shared Pagenumber as integer
public dim currentgroup as string
public shared dim offset as integer = 0

Public Shared Function getInvoiceNumber() As Integer
        Return  invoiceNumber 
    End Function
    
Public Shared Function setInvoiceNumber(invoice as integer)
       invoiceNumber=invoice
    End Function

Public Shared Function getCurrency() As string
        if chargeNum <> invoiceNumber then 
        currency ="C"
        else 
        currency="N"
        
    end if
    chargeNum=invoiceNumber
    Return currency
    End Function```