Using If and Else statements in Ruby

Very new to the world of programming and just starting to learn, working through Flatiron School prework and have been doing ok but unable to understand "if" and "else" statements for some reason. The problem is similiar to Chris Pine 'deaf grandma' problem but without saying "BYE!" three times.

~The method should take in a string argument containing a phrase and check to see if the phrase is written in all uppercase: if it isn't, then grandma can't hear you. She should then respond with (return) HUH?! SPEAK UP, SONNY!.

~However, if you shout at her (i.e. call the method with a string argument containing a phrase that is all uppercase, then she can hear you (or at least she thinks that she can) and should respond with (return) NO, NOT SINCE 1938!

I have so far:

def speak_to_grandma
  puts "Hi Nana, how are you?".upcase 
  if false  
puts "HUH?! SPEAK UP, SONNY!"
  else 
    puts "NO, NOT SINCE 1938!"
  end
end

but am getting wrong number of arguments...how am I supposed to add argument while using the if/else statements? This is probably a very easy and basic question but can't seem to get my head around this (overthinking probably).
Any help and clarity would be greatly appreciated.