vodacom *********** account service ,billing

i have a cellphone contract with vodacom and it is a coperate account firstly i got a bill saying i owe 4000 and when i enquire i was told that was for data,but that was impossible as i had a black berry using a bis .my phone has been soft locked ,but the amount keeps on increasing and at this moment it is sitting at 12000 and i do not understand how much is the interest rates and my life is messed up due to this