Vodacom in breach of their specified payment terms

I have been a customer of Vodacom for 20 years. I have only used Vodacom and I have never defaulted on a payment. Recently, my debit orders from my very old account bounced as I don't make use of that account. As soon as I was aware the debit order bounced, I immediately paid my account, usually within 3 days. One day a lovely Vodacom person called me to notify me that I had not made payment and said that they will take off the debit order on my contract account and I can pay in manually each month. Since then, Vodacom's automated call centre calls me ever single day from around the 20th of each month, stating that I have not yet paid my account and I need to pay to avoid a disconnection. Well, the Terms of my payment on my invoice that I still receive each months states: 'Always remember that your account is due by the last day of each month. If your account is not paid by this date, your line may be locked.' Yesterday, 24 September, Vodacom decides to lock my account. Noone to answer my call as it was a public holiday and 'out of office hours' so no-one could solve this for me. I got extremely lost in a location with my young child because I could not access my data. 1) Why did my line get cut for no reason AT ALL? I am NOT in arrears and there's still 6 days until the last day of the month. 2) Why lock my phone on a day that is 'out of business hours' so there is no way for me to resolve this immediately? I am very disappointed with Vodacom and my contract is due to be renewed with them. Why do I want to do business with a company who is in breach of their own terms and after the very unnecessary stress that they caused for me on the 24th.