Harassment from VVM MTN

I wanted to cancel my contract with MTN, however, cause I still owed money they said that I would need to pay my account up in full before I could close my contract with them. In Jan 18, I emailed MTN legal department asking what was the outstanding amount to which the response R3739.03. To there I rep**** asking is I could please pay this amount over 2 month (End Feb and End March, amount being R1869.515) as I having financial issues and they agreed. I HAVE ALL CORRESPONDENCE ON EMAIL!!!! Towards end of Feb, around 19h30pm (note here I am just preparing my children for bed and outside of my working hours and this is my family time), I received a call from a man calling from VVM asking me about my account with MTN and wanting me to confirm personal details etc. I refused to give my personal info as my contract is with MTN. I explained to the gentleman that I have a payment plan in place with MTN and not sure what is the reason for his call. He refused to listen to my story and said that it is not his problem as MTN handed my account to them. I ask the man to please call me the next day (during working hours) and I have 18month old baby that was crying and needed me to attend to her. The man refused to listen to me and said he does not care. He wants his money. I refused to talk anymore and just put the phone down. Not shortly after that, I received a call from a lady from VVM to ask me why I put the phone down. Now being upset, my children are upset, I told the lady that I do not appreciate being harassed and I am aware of my debit owing and have a payment arrangement with MTN. She herself did not want to listen to me a started laughing. I told her I am going through financial issues and that again I have a payment arrangement with MTN and I will take this up with them directly. I e-mailed MTN's legal department and sent a message on Facebook about what happened. MTN rep**** and said as soon as the proof of payment for the first installment is mailed to them, they will advise their debt collectors to close my account. Proof was emailed to MTN's legal department. On the 7th March I yet again received a call from VVM demanding money. I had told the woman that I have done payment and the proof was sent to MTN's Legal department as instructed. She told me this is wrong and I need to send her the proof, which I did with my whole correspondence with MTN's legal department from beginning to end regarding my payment arrangement with MTN. The email address I mailed to was ********** I have not heard anything from the 7th March until today. Another lady has called me from VVM. I told her I will not confirm my personal details and that I have a payment arrangement with MTN. She told me that my payment to MTN is not valid as I was to pay VVM. She told me if I do not pay R2000.00 today, she is going to blacklist. I told her that is wrong as my payment arrangement was made in January already and I do not know why my account was handed over to them. I told VVM that I would call MTN as I am tired of being harassed. VVM lady tells me she does not care and she will keep phoning until I have paid VVM. I eventually put the phone down and have unplugged my phone. This is truly harassment and emotional abuse. Being threatened if I do not pay today, I will be blacklist. I have made a payment arrangement with MTN directly, to which I have all correspondence for. I have paid my first installment and my last end of March.