*********** help line and network systems

I am on prepaid on cell c. I used to have a contract with them about 8 years ago before migrating to Vodacom. I have now ported back to Cell C and was on the 66c prepaid plan. Without asking me Cell C changed me to the all in one plan. I have tried on self service to change back. I get a message that it failed. I call your call centre and your prepaid department says they still see me on contract. Your contract department can't help because they say I can't tell them the last 4 digits of the credit card that expired 6 to 8 years ago. A week ago your prepaid department said they would esculate it for me as now its showing my number as permanently deactivated I have tried to post my number to a different network and I can't to do that because cell c won't release the number. I have never seen such incompetence in all my life!