Upgrade Cancellation

Very poor service received when dealing with Cell C. I received a call from their consultant regarding an upgrade. They advised on a deal with an A52 cellphone. I was advised 2 weeks or 21 days for delivery. My current contract ends 12 July 2021. To date I have not received my new phone as they don't have stock. I have been to their Overport outlet to see if they can assist. Unfortunately the upgrade has to be cancelled on their system. before they can assist me. I have made numerous calls to cancel the upgrade but they claim its under investigation. What are they investigating when they don't have stock to supply their customers. I cannot choose another upgrade as they are not assisting in cancelling the previous upgrade. I requested to speak to their manager and I keep being told they have flagged my complaint and a manager will call me. Not sure what to do next.