Please cancel my contract end of may... 4th of may...Boom your out!!! but lets still bill you anyway...

End of April i signed a request to cancel my contract 31 MAY 2016, so they took my money end of April and by the 4th of May the contract was put over to pay as you go and the subscription was gone... when I called into the call centre the woman said that I pay end of April for April's subscription and for march's call cost... now I really do not know if you might think that I was born under a rock but I paid a month in advance when I opened my contract in 2012. now the 4th of may I was switched over to prepaid without any warning and my minutes, data and SMS's was taken off my phone leaving me stranded in the middle of Johannesburg. none the less this morning I opened an email WAIT FOR IT... with my new STATEMENT and you are charging me again??????????????????? I had no choice in going over to GLOCELL but this is pathetic!!! I want my money back I paid the last month because I didn't get any subscription benefits and I WILL NOT PAY END OF THIS MONTH!!!