Cell C still bill you after clising your account

At the end of August if I am correct I went to the cell C shop in Hazyview and told them I want to terminate my contract and the gave me a full comprehensive quotation of the full amount I must pay to end the contract on that day. I then immediately oayd the amount and my control was terminated and the person who assisted me assured me the account was now closed and my number *** was converted to a pre paid number as from that day. Today I get an sms stating I am owing R153. 92. It is due 31/10/2020. Acc ref number is:

Dear Valued Customer. As at 01/10/2020, your Cell C bill is R153.92 and payment is due on 31/10/2020. Your account reference is ***. If you have already paid, thank you. Cell C

What is this?? I didn't receive any statement except the printout from your cell c shop stating there is a zero balance and that my account was paid up and terminated.

Explain please.