Double deducted

i made an online purchase of R827.80 on the 27/11/2020 of which was successfully deducted from my bank account, on the 06/12/2020 the amount of R827.80 was deducted again on my bank account which means they double deducted from my account. i have been in contact with them via their CHAT with no assistance. im really frustrated with the kind of service they are giving me with not giving me a straight answer as to who s suppose to refund me between them and the bank. i never had this kind of problem with any other online shopping. and its not the first time they did this to me. ive contacted my bank and they need a letter from zara confirming my one purchase on the 27/11/2020. which they are refusing to give me. if i dont get a reponse from them i dont mind going as futher as i can get. cause they are robbing people with these double deduction.