Bad service

My dad had an African Bank loan in 2015. As the monthly installments went off by debit order he was insured that the Bank get their monies. As my dad is 85 years old there is no way that the bank can give him a loan of R165 000. I see this as rectless lending. How on earth can a pensioner of 85 years qualify for such a huge amount. Now after two years African Bank is harassing him with threatening sms's stating that he owes African Bank that amount of money. My dad is deaf and suffering of demensia so he is not aware of any contract that he signed with the Bank. This is a serious matter as according to the NCR African Bank indebited my dad at the age of 83. His id is ********** 050084