Mtn still ***** from me.

On the 20th May 2018 I requested for an upgrade to be done on my ********** 391. I was told that the phones will be delivered within 7 working days. It never happened. Seeing that I called in and requested for the upgrade and my contract to be cancelled and was advised to send a cancellation letter to ********** which I did on the 1st May 2018.Thandeka told me that they will only cancel my contract as soon as they receive the phones back to their warehouse and those phone did not even reach me.My contract was not cancelled as i was billed on the 25th May. I sent another email and it was ignored. On the 5th July Wiilem Jnr Joost sent me an email asking me for the cell number in question as well as my ID which I gave him and nothing happed. The 25th July was billed again and I then sent another email to Willem Jnr Joost and he just ignored my email because I was billed again on the 25th August.I want to know if I must be billed for something that I did not receive or use.Is Mtn gonna keep debiting my account and have me blacklisted for the service they never rendered to me .I need to know what must I do as I am very angry and frustrated because it clearly shows that Mtn does not care about people but themselves.They promise to resolve my problem but nothing is done.