Standard Bank Worst Bank Ever

I recently settled my revolving account with Standard Bank and received my paid letter; shortly thereafter, they began sending me summons for the overdraft account, for which I made arrangements and am currently paying. What irritates me is that arrangements for paying the outstanding balance on a monthly basis are still in place, but Standard Bank harasses me with summons demanding that I settle this overdraft all at once, which is totally unacceptable given that this is due to their wreckless lending criteria, and as such, I do not have such money to settle this account all at once