Rainbow Finance *****sters!!

Last year around September I approached House and Home Fourways to buy a fridge, financed by Rainbow Finance. When signing the contract I asked for my account to be debited on the 27th of each month. To my surprise when I get the contract they put the 1st, so I immediately asked the person assisting me to change that, he then told me that unfortunately it can't be changed on the system and I shouldn't worry about it coz they can't change it, Rainbow Finance sends them the contract just like that. I signed the contract as i was desperate for that fridge and was assured that the date is not a problem. Next thing now they want me to pay two debit orders for one month because they put the 1st on the contract. So basically I must pay on the 1st and on the 27th of the same month! This is *****! Why put the 1st on the contract if it can't be changed? Consumers should be able to choose on which day their accounts may be debited.