Wrong Order !

I was assisted by a cashier to redeem 2000 worth of points for a Small Watermelon Mcfizz. After having completed the order. Shortly after that the lady from the kitchen called out my order number and handed me a passionfruit Mcfizz and was told they ran out of Watermelon. The lady then walked away , without listening to whether or not i was going to accept this order or not. I feel that it was really unfair and unprofessional that i had to redeem 2000 worth of points for something i did not ask for.