BAD CUSTOMER SERVICE

I bought a fridge online on the black Friday week sale at HiFi Corp to be collected at their Mazimtoti branch mid December as i am working in Gauteng and the fridge is for back home in KZN. I paid for it there and then and it was reserved for me. I then contacted the customer service to extend my collection date and we agreed to the date. Three days later i receive an email saying the fridge is out of stock yet it was reserved after my payment. I then contacted the customer services and the guy that i spoke to said he will investigate and get back to me, till today i never received his call. I then called again and i was transferred to the store manager, she told me she is expecting stock and will call me before the end of the week. Its almost the end of the second week and still nothing. I contacted the store this morning and said they are still awaiting stock. What i don't understand is that i have paid the full amount, how come my fridge went from reserved to sold out. Why didn't they keep the fridge because its fully paid meaning its mine now.