UNPROFESSIONAL and CRUEL

I lost my job 3 yrs ago & informed Standard bank about it. I continued paying both my revolving credit loan as well as credit card with UIF. When it stopped I couldn't pay anymore & my account got handed over to Brodkin attorneys. On 13 September 2022 Brodkin sent a reminder that I should pay R2400 on my account Ref SR556962 which I did. To my surprise they sent an sms on 04th October saying my last payment was insufficient & I must pay R2900. I'm still unemployed & paying using my 5 yr old autistic son's disability grant. Where tthe hell am I supposed to get extra R500 when they are the ones who told me to pay R2400!!!!!!!?????