Incorrect information given

On the 8 October 2015 I called the customer service number to request a change of date for my debit order from the 26th to the 1st of each month and if I had let them know early 3nough in the month. I was reassured I was, however I was told I was told that my debut order would go off on the 26th October and then again on the 1st of November. When I asked why I was told that I would be in arrears if that did not occur. I then wrote to their support email on two occasions and have to date had no reply. I phone the next day and was told by a different woman that my date could be changed and asred me no debit would be taken off on the 26th. It did and was returned. When I called to query a 3rd person told me I had to give a months notice??? When I asked to speak to a supervisor he was unavailable??? She could not give an answer as to why my emails were not responded to or why I was told 3 stories. I asked that the supervisor listen to our conversation and respond in writing. This was Friday. It is Sunday still nothing. So how do I ensure my credit rating not affected to their incompetence and how do I now pay this month what I owe?