Contract Cancellation with MTN

I had to contracts with them…the router and the sim card, I cancelled the router and paid a fee of R1 845.24 and that was the amount they told me about that I had to pay… this month they were suppose to deduct only R300 but instead deducted R1 187.50 plus R59.00 of God knows what then when I called they tell me that I was suppose to pay R2000 and something those ones at the store were suppose to tell me I’m so angry for the inconvenience I didn’t budget for this amount!! MTN is a ****!!! Nxa