Legal Costs on Arrears

My account has been in arrears, less than 2 instalments, and I have been paying more on top of my instalment (R3300.00) to bring it up to date. The day I paid enough to reduce the arrears to less than an instalment (R2000.00), Wesbank decides to add legal costs of R3500.00. This is really absurd and it seems like they just don't want a customer to bring account up to date. How can Wesbank decide to add legal costs the same day a payment is made? Now my account is owing more than R6000.00 because of legal costs which I have no idea how they came by. I was not served with any summons or anything. Wesbank must reverse these costs.