MTN service provider giving wrong package and not cancelling it when requested to do so

Last year around October I went to MTN store to apply for a data and WiFi router contract,they took my docs and told me they will call me back once it’s approved since they are having problems with the network/server.The following day I got a call from MTN people offering me data deals,I thought it’s the same people from the MTN store since they had said they will call me so I told them that I want data and mobile router not just data and that’s the package I agreed to with them so the package was delivered to me via courier only to find that it’s the wrong package since it was only 2 SIM card with no WiFi router,so I quickly went to MTN store to tell them that they sent me the wrong package.At the MTN store they told me it wasn’t them it’s the online MTN service so they helped me to call them and try and cancel that contract since it’s the wrong package so I spoke to them on the phone n they told me the contract will be canceled within 10 days,after 10 days I did follow up and they even sent me proof via email to show that it’s been cancelled.fast forward month end my account was debited with 400 which was not even the amount we had agreed to for WiFi router plus data instead it’s double the amount so I had to reverse and I called them to find out why they debited since it was never activated and I got the wrong package and cancelled it same day? Another lady helped me on the phone and told me they canceled it I even received sms’s Confirming that now I’m surprised because it’s month again and they still debited the 400 ,I have to reverse the debit order again and this thing is messing up my credit record wheareas it’s something we never even agreed to.Can this be fixed please because I have done all I can but not getting any help with this...