SHEIN complaint: Undelivered order

I made an order at the end of August delivery was marked with a date of 13-16 September I was supplied with a tracking number that did not appear with any courier and the status constantly remained as in transit the due date passed and I was told to wait patiently for another week to take the date to 24th sept. Again the date passed and still no delivery. I wrote to shein explaining the urgency of receiving this order and made it clear to them that was the reason I had ordered so early allowing plenty of time, they told me not to worry and they would do all they could for me , so far they have done nothing but come back to me constantly with generic emails and never answer my questions fully I have reasonably asked them to resend the order by express delivery they have told me that they can not change the shipping information to express as the system does not allow, I asked to be passed to management but still they just reply with generic emails which have a 48hr turn around time on them , therefore causing more delays . I am not asking for anything out of the ordinary I just want to receive my order before I have a flight booked to leave the country and request express delivery over standard delivery as a good will gesture for my time wasted sitting patiently for them to do absolutely nothing