DMC Holiday Club trying since 2010 to stop the holiday club from debiting money from my dad's account

Please can the debit order STOP NOW my dad is a pensioner and I have send a letter to them on 2010 to stop the debit order and still they are trying to debit allkinds of different amounts from R1700 to 656 to 200 ect.... my dad is not working he a pensioner and they trying to take his last sent that he must pay for a roof over his head and then some food as well. I am going to take this further because my mother also said to them to stop it because they do not have money to pay for the DMC holiday club and yet they don't listen!! Every month DMC are putting my dad under more and more stress and he is not a healthy man he had 3 triple bypasses and after that 4 heart attacks and a stroke last year and yet while my dad was in hospital my mother got calls. STOP PHONING MY DAD! and STOP taking money they already said they DO NOT WANT IT! I would also like to get a legit email address where I can email a letter to STOP this debit order! it is ridiculous to see and hear how many people are targeting the pensioners to take there every last cent.