Non adherence to instruction

I have been having debit order issues for the last 3 months . I changed my account from savings to cheque and I phoned telkom and notified them in advance of the change and gave them my new account details . The first month they tried to take money from they wrong account on april the 25th so it bounched. In Mei and in june the same problem persisted . I have phoned back 3 times to sort the problem out and they cant tell me why it keeps hapening . Im not going to phone back every month and ask them to do there work properly . I had to pay by myself the last 3 months . Id - *** cell number in question - ***