MBD and Woolworths harrassment

I was behind on my Woolworths account due to unforeseen financial circumstances and my account handed over to MBD. I made a payment arrangement with MBD which I would make payment manually with the agreed upon amount. I would however recover phone calls daily even though I kept to my payment arrangement. I was then told that I would continue to get these phone calls until I set up a debit order which I eventually did as I was getting harassed numerous times a day via my work and mobile number. I have not missed any payments however the phone calls have further intensified with them demanding I settle in full. I have since doubled my debit order amount which is more than 10% of my outstanding balance around 13%. Since then i have continued to receive numerous phone calls demanding i settle in full. More than 1 call per day, sometimes up to 4 times. This is harassment and completely unacceptable especially since my continued compliance with their demands thus far.