WHAT IS THE ISSUE, RELEVANT LAW, APPLICATION AND CONCLUSION OF THIS LAW ?

Anna called Harry Textiles Ltd to make an order for to buy a red dress for $50, the manager said only blue dresses were available and they cost $40. Anna said because of the inconvenience she would buy the blue dress if it was sold to her for $20. The manager didn't hear her because there was noise in the background, there was a problem with the phone and then the phone suddenly then went off. The next day, Harry Textiles Ltd shipped the dress with a $40 bill and they want to take Anna to court because she has refused to pay for the dress. Advise Harry on whether they can recover the money in court.