Standard bank student achievers being switched without my consent

Today I received a call from standard bank telling me that I owe more than R900 for a student achievers account that I opened in 2018 that I don't use. In 2018 I got hired by Homecoming events to be an embassador for standard bank student achievers account and the young professionals account,basically I had to let students around my campus know about these accounts that standard bank offers.

One of the conditions to get paid was for all of us(embassadors) to open student achievers accounts and I opened one at Maponya Mall standard bank even though I had a standard bank current account already. The lady who helped me told me about the R5 monthly charges and I understood that. We got paid once for the job and I never used the account(student achievers) after that as I was happy with my current account so I even forgot that I have the account.

My problem is not the R5 charges that may have accumulated but rather the R70 charges that standard bank started charging me when I turned 24 as I did not qualify for a student achievers anymore. Why did they switch my account without informing me as they always inform me with any changes concerning my current account? Now the R70s have been accumulating and they are only telling me about it now? I even tried to understand and said that I want to close the account and I'll pay the account monthly as I cannot pay the full amount right now and they said that I have to pay the full amount first if I want it to be closed. This means that they will continue to deduct the R70s going forward and this is completely unfair. My experience with Standard bank has been smooth all along until this happened and if they are unable to fix this I will leave them and go to another bank that won't rob me with like this.