Online purchased item never delivered to me

I purchased a cellphone online on the 28th and my delivery was scheduled for Friday 02-08-2024.I rescheduled for Saturday 03-08-2024 since then I haven't recieved my parcel and when I call the helpline I am being sent from pillar to post,I sent emails and done everything I could but nothing seems to help.I do not know what to do next.