Harassment by RCS Group

I am being harassed by the RCS call centre due to ,according to them an account that is in arrears. I have sent a number of emails and proof of all my payments to their required email address nl. ********** , but still the RCS group call centre call me every night , by the rudest people alive to tell me every night that my account is in arrears! I am tired of sending proof of payments to the RCS group ,because I just know that another *********** rude employer of the RCS Group is going to phone me again! Please assist me in clearing up this problem. As I look at other complains against RCS Group ,it seems to me that there is a high level of incompetence at RCS !