harassing me over R21

I cant believe you people, I have been a dedicated customer for many years, All of a sudden I short pay R21 and its a ****** heart attack with you. Sms's , Phone calls, threats to cut me off and black list me and attach my property, what the hell is wrong with, To top it all my account has not been credited with payments made. I want this resolved asap and quit harassing me with *******, I have never missed a payment and you treat me like a damn ********. These contracts run out and you can all go to hell if thats how you want to treat me. GREEDY AND *******!!!