A new contract sneaked into my account without my permission when I called in to cancel a contract

My cellphone contacted ended in June 2023 and I call in the beginning of July for my number to be ported to prepaid and the contract to be canceled. I then confirmed with the lady that I will not be charged for anything on this cellphone in July, she confirmed that only R18 will be charged and the cellphone contract will be closed. I received an invoice in August and saw tha she sneaked in another contract of Watsup data on the same number I asked to be canceled, and amount of R235 monthly. I had to call again to remove this thing of watsap data asa I never requested for it. The lady then said she requested a refund for that, I do not want to be billed for tha as I never requested it and do not afford it. It will mess up my finances, I’m currently on martenity leave with a newborn and do not have time to follow up on these things.