Contract *****

I had a 36 months contract of with you guys that ended in March and ever since then I've been trying to cancel with no assistance and last month was told I need to pay R1200 because I didn't cancel and I did exactly that and bow I'm being told that I owe R1800.00, please kindly explain to me where does the R600 come from not to mention the R1200 that I have to pay. Please by God's grace kindly cancel my contract and stop messing up my name.