Poor service and system issue

In the past 2017 and 2018, I had a problem with Telkom debiting my account around the 18th and 19th when my pay day fell on the weekend, I did inform them that my salary day is the 20th even when it falls on a weekend I still get paid on the 20th not before that, Telkom then promised to debit on a Monday after should my pay day fall on a weekend since their system doesn't allow them to debit on a weekend and I've been happy since then, then this year in April, the 20th was on a Saturday, the following Monday was going to be the 22nd.. I then made an eft of R750 even though I owed Telkom R743, later that afternoon Telkom then debited me even though it was on Saturday, that was new to me however seeing that I had made an eft earlier I then reversed the R743 that they had debited, the next invoice that they sent beginning of May stated that they were going to debit R943 on the 20th May, I called in to query, after waiting for more than 20 minutes the lady that I spoke to assured me that the payment of R750 was reflecting on the system and that those charges were going to be reversed then I had to wait for a reference number; after 10 minutes of waiting on the line I had to go back to work and I was forced to hang up, the 20th of May came, Telkom decided not to debit, I waited. Calling them did cross my mind however life gets busy and I ended up forgeting. I didn't make an eft in May due to the fear that they might debit again; and I'll end up reversing and being charged the "back out or black out fee" whatever they call it. then on the 4th of June I received an invoice stating that my account is due with R1668.18 and it'll be debited on the 20th of June; I spent the rest of the day trying to call Telkom on 180 but there was no luck; I finally got hold of them today and spoke to an agent who told me that Telkom didn't debit on the 20th of May due to system error but insisted that I'm still liable for the charge of R199, I then asked to speak to her Manager, she put me on hold for 7 minutes then later I spoke to a guy by the name of Tumisang Sedio who said it's my fault that I reversed the payment in April; I then told him that I reversed the debit order because I had made an eft of R750, he said it doesn't matter but I'm still liable for the charge or that back out fee.. That wasn't my fault; I made the payment because of the fact that they don't debit on weekends and public holidays, I couldn't wait for the 23rd since I wanted to get all debts and payments out of my way and be left money that belongs to me; also them not debiting my account in May is not my fault, the funds were there and I can't pay double because of their system error..