Items not delivered!

I made an online purchase at Cotton On on the 14/05/2020 but have not received a delivery till now. When I contact them I am only told that my parcel has left their warehouse. My sister made a purchase on the 26th but has already received her delivery. This is weird... I don’t know how to track my parcel with the courier company coz when I contact them I only get through to an IVR which refers me to their website. Where I cannot use my Cotton On reference to track the purchase. At this point I’m genuinely annoyed.