Very bad service, unreliable

This delivery service is the worst, I placed my order at Shein on the 13th of November, they received my package from Shein on the 4th of December, it still has not been delivered, when I follow up they keep on saying they will escalate but no change. My sister placed her order around the 27th November but have delivered her package. They are not reliable, they cannot even explain why they are not sending my package out