Cell C, and how they sold a product they never had to begin with

I wanted to upgrade, and got a call from their direct office because I was due one soon. Heard about a great deal, including a powerbank! Cool!

So, once this is all done and sorted, I'm promised delivery within three working days. It took ten, but whatever, the phone finally arrived!

Without a powerbank.

Annoying, but I figure, this is just an error, right? So, I call in. Turns out, no, they figured that because they've run out of stock, they can just send it without one! And no, they don't plan to send a powerbank later when they're in stock.

"But, Cell C," I said (or rather, my very irate mother said, as by this point I was having an anxiety attack), "the powerbank is right here on the contract! You are required to provide it. That's what a contract means. No, it doesn't say 'while stocks last!'. It says '[phone model] + powerbank'. You have to provide what's in the contract."

"Well," Cell C said, "we can't." (Or rather, that's what they said after redirecting my mother's call through the same three or four departments about three times each).

We've asked to cancel the contract, and now have to wait four more working days (so, twelve working days, probably?) for the phone to be collected before the cancellation process can be started. Meanwhile, I'm going to be taking my business elsewhere. The only thing Cell C can do for me now to make up for this is to perhaps let me out of my current contract a month early so I can port my number. I don't want to do business with someone who sells me something they don't have, then tries to tell me it's my problem.