Still billed after contract expired and requested cancellation

How am I supposed to rate this business out of 5? This business deserves less than a negative 5-star rating.

My MTN contract expired in July 2015. MTN, with neither my knowledge nor my consent, simply migrated the expired contract to pay-as-you-go, and happily continued billing me.

I immediately cancelled the contract in August 2015, after calling MTN to inquire exactly how to go about the cancellation. MTN had stated that I should send an e-mail (to the address they then supp**** me with) , requesting the cancellation. I then did as instructed by MTN, thereafter considering the contract cancelled, as I believed I had been dealing with competent people....

I turned out I was very, very wrong... MTN staff are extremely ***********; they neglected to cancel my contract, and simply happily continued billing me.

I supp**** MTN with proof of cancellation, yet the harassment continues....

Now, two years later, they continue to hound me and send me threatening lawyers letters.

BEWARE OF MTN - THEY ARE *******. EVEN AFTER YOU HAVE CANCELLED AN EXPIRED CONTRACT, THEY WILL CONTINUE TO BILL YOU AND DEMAND PAYMENT!!

THINK VERY, VERY CAREFULLY BEFORE SIGNING A CONTRACT WITH MTN.