Cell C a ****!

Been trying for many months to cancel my cell c contract and convert to prepaid without any success. First get transferred to mutiple departments, sometimes get through to retentions, other times cuts. When retentions verifies my details says incorrect which is impossible. Ask to speak to someone whom I can forward proof their system is incorrect, told manager will call me and manager NEVER does. Went to Cell C store who verify my details are correct but can only help me with upgrade. They say I have to speak to retentions who cannot verify my details. Its a ****! I have been a customer with Cell C atleast 10 years, definitely longer! Please, please help anyone at Cell C!