Furious ABSA client

I'm writing this complaint on behalf of my mother. She has been an ABSA client for years, last year she went to the bank to free up some money from her investment account. She had a savings account with ABSA The lady that was assisting her offered to change her account to an old age account where bank charges would be free because she saw that she receives her old age pension on her account. She said she qualifies for the old age account because she has an investment with ABSA. A few weeks back she got a call from ABSA saying she owes almost R400 for bank charges and that she could use her overdraft to settle that amount owed. Which was a surprise because she didn't authorize an overdraft for her account. On Saturday she went to the bank and she was told that her account was changed to a cheque account and not the old age account as she thought. The charges that she owed was because of the cheque account that she was moved to. It is very unfair to expect a pensioner to pay almost R400 when she gets pension of R2000 a month. How can you change a pensioners account from a cheap account to a more expensive one. Can the lady who caused all this pay that money because she was chasing targets at the expense of a pensioner.