Settle and a month later sms's ,treats ,ect

I phoned Rcs and got a settlement amount from them and paid over everything, and 2 months later sms's and calls and treats, then they say R 500 what i pay and then months go by and demands and treats of summons and then they say its 300, that i pay and now again treats of summons , how many times must an account be settled, i refuse, just because your people dont do your job and wait for months to check payments and then interrest is added, stop harrasing me this is not acceptable.?..\Summons will be issued on your RCS Account. To avoid further legal action contact 011- ***.RF061850"