Double billing

I have been with Vodacom since December 2022 and I have never missed a payment with the.. Last week to my surprise I got a text saying that I owe them for last month payment and I will be billed double with a penalty fee for late payment. I called them and they advised that I should send a last month's bank statement.. I haven't gotten any help and they are planning to block my number! When I call these lousy consultants are giving me attitude or hang up on me!