Unused arguments while using ifelse in R shiny

in app.R in server function

server <- function(input, output) {

I have this reactive function which checks the radiobutton input and populates the input choice in select input.

var <- reactive({
    switch(input$selectBy,
           "cname" =  customers[,1],
           "cloan_num" =  customers[,2]
          )
  })

Now I wanted to change the label in the selectInput function based on radio button but I am not able to do so.

  ifelse(input$selectBy == "cname", lbText = "Select Customer Name", lbText = "Select Loan AC Number" )

in the above line I am getting

Error in ifelse(input$selectBy == "cname", lbText = "Select Customer Name", : unused arguments (lbText = "Select Customer Name", lbText = "Select Loan AC Number")

  output$selInp <- renderUI({
      selectInput("noc",lbText, var(), selected = NULL, multiple = FALSE,
                selectize = TRUE, width = NULL, size = NULL)
  })

Full Code:

ui=fluidPage(

  titlePanel("Title"),
  sidebarLayout(position = "left",

  sidebarPanel(
      fluidRow(

        uiOutput("selInp"),

        radioButtons("selectBy", "Search By:",
                     c("Customer Name" = "cname",
                       "Customer Loan No" = "cloan_num")),

        pickerInput("branch","Branch", choices=unique(customers[,4]), options = list(`actions-box` = TRUE),multiple = T),

        dateInput("endDate", "End Date:", value = "2018-12-30")
      )
    ),

  mainPanel()

  )

)

########################## server function ################################

server <- function(input, output) {

  var <- reactive({
    switch(input$selectBy,
           "cname" =  customers[,1],
           "cloan_num" =  customers[,2]
          )
  })

  ifelse(input$selectBy == "cname", lbText = "Select Customer Name", lbText = "Select Loan AC Number" )

  output$selInp <- renderUI({
      selectInput("noc",lbText, var(), selected = NULL, multiple = FALSE,
                selectize = TRUE, width = NULL, size = NULL)
  })



}

shinyApp(ui, server)