Promotion not honored

Homechoice promoted a special where one will receive 1x lace curtain free if you purchase a 5x curtain set worth R899. I purchase 4x 5 piece curtain sets worth R3596 and should have received 4 x lace curtains sets free. I however only received 1x lace curtain set free. This is unacceptable especially since I am a regular client who have supported Homechoice for a long time