A BUNCH OF ******!!!!

I've been with MTN for the last 4 years and on the 13th of every month i receive a statement except for November where conveniently my "black friday" contract ended and the price went back to normal and they didn't see fit to advise by sending the statement with updated figures prior to the end of my contract on the 22nd! Now i'm being told i need to provide notice to cancel a contract that ended