Bad service.

I took a bed from bedzone and when I signed the contract the agreement was for the last day of the month ..to my surprise they debited my account for December on the 11th which they sent sms for ctange of debit date I responded with the date of 30 of Dec which I'm comfortable with.. I called customer service, they tell me that can't reverse the amount. How do they expect people to live while they snatch money in one's account without their consent. They are ridiculous for not sticking to their agreement policy