Check what CPanel reports as your disk space. I've seen some differences between the account panel and CPanel. CPanel ultimately has control over what you have and do not have.
Now that you have been given a definite answer to your original question, and because you have not posted a response in over 48 hours, I am going to close this thread to mark it as resolved. If you need more help or have any additional questions, feel free to open a new support request.