Parcel not delivered

I have placed order on 28 July 2021. My order had only 4 items. On the 2nd I only received 3 items. 1 item is still oustanding. I do not even know where my parcel is. Clicks is not answering their call nor reply to their email. This is really inconveniencing me as on their site they say it only takes 1-3 business days to deliver. I need my parcel ASAP.