“Pay money first. I wrap for you” - the intention is to get the customer to pay for the item first before getting it wrapped.

The phrase “Pay money first”  is grammatically incorrect and the word ‘money’ is redundant.  “Pay money first”  also sounds rude and aggressive.

A More Polite Way To Say It

• “Please pay for the item first before we wrap it for you.”
  
  
• “You’ll have to make payment first before we can wrap it for you.”
  
  
• “I’m sorry but I can only wrap it for you after you’ve paid for the item.”
  
  You are apologising for the inconvenience you are causing the customer.

Source: Edited from the Singapore Retailers Association's Speak Good English pamphlet.