contract expired but im being billed every month.

my contract ended end of march 2020 however Telkom still bill me money, from april to date, now they are are threatening me to list me at the credit bureau. I have not being using the sim card and there is no data even in the sim card, I asked for them to upgrade they never came back to me,,poor service ever,,they must just leave my money alone please,,,i wont pay money for free to Telkom..