What on earth is going on with my account!!!!!

I have a month to month contract which I carefully monitor to ensure that I never go over and overspend on. Today I looked at my current usage and it says that I have airtime, day and night time data available, however I owe R986!!!! I felt sick to my stomach seeing this as I have no idea how this has happened, I haven’t done anything different than what I do every day on my phone. I my cellphone monitor usage hourly and daily and can see that this happened sometime between 14:00-15:30pm today!!!

I called into the call centre now and spoke to someone who said that I actually owe R1134!!! Please can someone investigate what on earth is going on!!!!