Billing errors

Im writing this review crying Telkom is messing uo my life, I am trying so hard to fix my credit record and telkom is just messing it up, I cant anymore I feel like dying. In December I paid up my contract in full they even debited over which the excess amount was later paid back to me but to my surprise the following month Telkom debited my account again which I then reversed because my contract with them was cancelled. TELKOM confirms that my contract was sucessfully cancelled but my billing date was the 5th of the following month with an amount of R100, now telkom is saying I owe R300 because I had reversed the R100 they debited after I have cancelled with them, SOMEONE PLEASE HELP ME WITH THIS I CANT TAKE IT ANY MORE IF I DIE TELKOM WILL BE RESPONSIBLE 😡😡 MY ID NUMBER IS *** 080 ***