Cancellation of services

I recently upgraded last month from rain 4G wifi to their 5G wifi service. If you go on their website it clearly states that it will be an automated switch over from 4G to 5G. After the 5G was delivered on the 14th of Oct , two of their consultants called me and I asked them both if my 4G would be cancelled as I did not want to be double billed. The one lady said not a problem it will be done no later than today or even better cancel it yourself on the app and you'll only get billed for the days used. I did as I was told. Fast forward I get my Oct invoice and they charging me a full price on the 4G plus pro rata of the 5G,claiming that I initiated the cancel hence I am liable for the cost. When I clearly had asked the lady regarding the cancellation of the 4G and she told me to do it and I wont be charged.