Vodacom can't pay back the money.

Just to share my story. I took a contract with Vodacom on 24 of March 2020 and when I received my ohone I wasn't happy with it, so I decided to return the next day because of they have a 7 day cash back return policy. It has now gone 4 months since I returned the phone and canceled the contract and still I haven't received my money back. I've called multiple of times and have heard that your money will reflect in 7 day. I've done this for the last 3 months and nothing has been done. Why do big companies do this? Why can't they just do the right thing?