Denied cancellation

On the 04/ February/ 2024, I paid in R9004.46 to close 3 lines. No invoice was sent to me during February and on the 25 of February no debit order went through. Today I called in since I did not receive my invoice on the 03/ March/ 2024 which is payable on 25/March/2024 only to be told that I am owing R5900 almost twice from what I was paying before I prematurely cancelled 3 lines R3600. How did they get to this amount? I have e mailed the proof of payments per line to cancellation department as required and as of now the 3 lines are on prepaid effective 01/March2024. What a *******, after being their loyal customer for more almost 2 decades.