Wingstop

Ordered 15 piece and paid for them. Only received 10 piece. Had already battled the commute home for 30 minutes. Cashier asked me what did I want him to do. I asked to speak to manager. Manager said I could come back or they could give me five free wings next time I am in. I don't understand how wings I have already paid for and not received were considered free. When I asked about the owner, he hung up the phone. I am now our money and wings. Picture is of what my order came as. I ordered wet wings.