Bad experience - saying one thing and doing another

Unfortunately I am under debt review with debt busters. I had to change my banking details and I informed Debt Busters and signed a new mandate for payment instruction, after which they sent me a confirming email, stating that they did receive the change in banking details and will make the necessary changes on their side (email received from a Client Service and Retention Consultant of Debt Busters) TO NO AVAIL. NOTHING HAPPENED. NO CHANGES WERE MADE. Now there is a dispute and guess who is at wrong? THIS KIND OF SERVICE IN UNACCEPTABLE IF THE FAULT IS ON THEIR SIDE! I am a very angry customer and will not recommend them to anyone. Stating one thing and doing another... sorry, that does not fly by me.