Double debit order on my home loan...I'm not Rockerfeller

Last week I contacted Standard Bank home loans to change the debit order on my account to the last day of the month, currently Standard Bank Home Loans have changed the debit order date to the 3rd of the month, without my consent and now calling me 8 times a day to find out where the outstanding money is, I have explained, I earn one paycheck and can't afford a double debit order and that was the reason for asking for the debit order to be changed to the last day of the month, not the 3rd as their staff did and as it reflects on their system. On 3 of the 8 calls, I have asked for a reference number so this matter can be resolved, at the same point on 2 of the calls, the consultant hangs up...is this really how you do business, the type of people you employ and how you treat customers? This gross inefficiency is astounding and I want this mess sorted out immediately, without anyone putting the phone down and expecting something that was not agreed! Go listen to your recording before making these calls and upsetting customers unnecessarily!