No delivery or communication

I placed an order on the 18th of December for a pair of sneakers, got a confirmation saying it will be delivered by no later than the 22nd. I then place a second order for another pair of sneakers on the 20th with an arrival date of 23rd. The second order actually arrived on the 22nd but I still waiting for the 1st order. It's been more than a week, I've tried calling the call center, was promised it would be delivered yesterday. it's now the 29th and I still don't have it. Did my sneakers grow some legs and run away? Unacceptable. Orders are #598068 (the missing shoe) and the one I did receive #599000.