Tired of Viatek harassing me

I have an incident with Viatek currently where they have contacted me to purchase some of their cartridges. After numerous calls where I kept telling Nicoleen that I will have to get authorisation from management and I have sent back a cancelation mail 2 days after receiving the quote (she said you have 7days to cancel), she chose to ignore me and send the package without me signing or agreeing to the purchase. I send the package back since I have sent the cancelation mail in time and did not sign for anything. A few days later she phones me asking if I was there when the package arrived, I said to her yes I was but sent it back as I cancelled within the 7day period, she ignored me once again and kept saying she never received the mail and they have a policy of not taking back items. The more I tell her that I cancelled in time the more she just tells me they don't take stock back and she did not receive the mail. She then again got the lady to phone me to confirm delivery, I asked the lady if she can remember that I told her that I need authorisation and she said yes, I then asked her if she received my mail where I cancelled the order and again she said yes and she forwarded the mail to Nicoleen. I then said that Nicoleen said she never got any mail and therefore I need to take the parcel as they don't take stock back. I then said to the lady I do not want the parcel. She then said maybe there was an internal problem with the mails and there fore the reason why Nicoleen never received it. I then told her that it is not fair if they had a problem that I'm now forced to take the parcel. I was then told that it's not that bad, the first payment is only due in January 2019. I said to her it doesn't matter when it is due, I personally can't afford it and my manager is not interested. So once again they send the parcel to me. I this time round printed and attached the cancelation mail with the whole explanation as to why I'm sending back the parcel. Again Nicoleen phoned to ask if I received the parcel and again I said to her that I sent it back with my proof of cancellation mail attached. She just kept on talking and saying they don't take things back and that they have on record where I have agreed to taking the parcel so I then got upset as she just keeps on being persistent and does not listen to me or give me a chance to talk like all her previous calls so I said to her "you can go back to your recordings and you will hear that I said I need authorisation from management but once again you just keep talking non stop and hence you don't listen to what I'm saying and that is exactly how this mess started". She then asked what mess am I talking about, so I said this mess that you keep sending things after I told you I need authorisation and after I told you the previous time that I cancelled in time. She then started again with she never got the mail so I just said to her, I sent my proof and therefore don't want to hear from them again or receive a parcel again and put the phone down. She is so persistent she sent the parcel again, I told the courier guy, sorry I did not order this, he can take it back. Now Nicoleen keeps harassing me with calls and just don't want to stop. I am really getting frustrated and don't know what to do no more as it does not help talking to her, she just keeps talking and does not give one a chance to speak and just does not want to except that she made a mistake.