No stock after 52 days of paying

Bought a stove online on the Builders Warehouse website for my mother who lives in an old age home and who's old stove broke. After paying the builders warehouse store phoned me and said that they did not have stock. This was on the 10th of May 2021. It is now 52 days later. Today I was informed by the branch that I have to pay an additional R1200 for a stove that they do have in stock. Builders, sort this out. This is a head office problem, not a store problem. You cant sell items on the website that you dont have. My mother needs a stove. Order number ***