Harrasment\threats

I keep on getting threatning sms's about not making payment arrangements. I only communicate via email with helen. Ive sent her in Jan\feb what i can afford to pay. She is clearly not doing her job. As for Im still being harrased and threaten. I make the payments as how i can afford. Got a phone call in march from one off the staff members of Groenewald and Lubbe telling me i must pay more. Who the hell does this company think they are?