Extra debit charge on my telkom contract

<p>This month Telkom simply charged me an extra R300 on my account- Almost double the nomrall monthly debit.</p> <p>I dont understand how this is possible as when my data is used up for the month on either contract I have with Telkom I can not use the internet and it is a closed-end contract. Ive emailed their accounts department with no reply.</p> <p> </p>