Damaged fridge shelf

In July I bought a fridge from Pick n' Pay Northgate. When I received it, one of the shelves was broken. I called Pick n' Pay customer service, who put me in contact with the branch. They said that they would replace the shelf but they needed the invoice number. I tried to call back a few days later with the invoice number but no-one was answering. I called customer service again and was told that the Northgate phones were down but they would get someone to contact me. Someone from Northgate then called, I gave him the invoice number and he said he'd get back to me. That was a few weeks ago and I haven't heard anything back. I emailed Pick n' Pay to get an update but I'm not getting any response.