No response from Cell C

I want to launch a complaint against cell c regarding my account. I recently received an account of R47 000 from cell c. I have written several mails and made several phone calls. No one comes back to me regarding this matter. They, are now threatening me to cut my telephone. I visited Thailand in Dec/Jan. I go there every 3 months for business. According to cell c my data roaming was on, according to me I cancelled data in 2013. I have a limit of R750 on my account. Could you please assist me in this matter.