Online order poor service

I ordered a trampoline on the 18th of December knowing my kids Christmas present might be a bit late, when ordering online you cannot order an item that's not in stock... so obviously with a successful order placed it should be in stock, phoned the 24th 5working days later to be told there is no stock my husband then phoned and was promised that there is stick in the shops near by and they will source the item and deliver, phoned again last week and was told its in the warehouse to be shipped with a tracking number provided in the next day or two.. phoned again this morning to be told again its out of stock. This is unacceptable I want this resolved immediately