Account in arrears.

My Vodacom account is payed every month via debit order. All of a sudden I get these SMS's telling me that my account is in arrears and I have to make a payment to avoid legal action and so no. So I went to a Vodacom shop to find out what is going on and they told me that someone at Vodacom changed my account from debit order to cash. ***????? I never asked for any changes Vodacom!! So now my account is still in arrears because of a Vodacom slip-up. Vodacom, I expect from you to fix this and contact me to inform me that everything is the way it was, including my account status, because it is time for me to upgrade and now I can't get a Samsung anymore but only a cheap ****ty phone.