Vodacom upgrades cheated me

I called vodacom trying to cancel my contract. I was then convinced to upgrade my contract. During the process the consultant indicated that Samsung has three a03 phones I opted for one that has three cameras. He then indicated that they don't have that one in stock and then I opted for two camera phone. I was surprised when I got the one camera phone. I phoned vodacom upgrades and cancelation department the next day and i explained my problem. They agreed to take the device back. Nothing happened. I phoned again after a couple of days when I didn't hear from vodacom or the delivery company. I was promised once again the device will be collected. Ten days after delivery still no collection, I get a call from consultant who help me with upgrade checking if I'm happy with the contract/device. I tell him story he speaks to his manager then tell me about the 7 days cooling period. I don't understand how I am expected to pay for their mistake. It's as if they waited for the 7 days to pass then call me. I don't want this phone If they can't change it they better cancel my contract at no cost It's not my fault.