Contract Cancelled

I have been a contract customer with Vodacom for over 20 years. Recently I was offered an upgrade, but they didn't have the selected device in stock. So I said , please cancel the upgrade as I wasn't keen on the other devices offered and will decide later. The agent cancelled the contract instead. I called the next day to say that I just wanted the upgrade cancelled not the contract. They said they will fix it up. Today I get another message that the contract will be cancelled at the end of the month and converted to prepaid - which is tomorrow. I claim expenses and this does not suit me. Are they driving a longstanding customer away or is this pure incompetence?