They gave me more then 40 GB on December after they said I owe them without any of my signature or my agreement with them after they block my phone number

They gave me more then 40 GB on December after they said I owe them without any of my signature or my agreement with them after they block my phone number. And it makes as bad person who doesn't pay the credit and I don't know anything about there credit account so they want me to more than R1000 of which I have never open any credit account with them. Can you please help me to fix that think