Charging me double

Rain has perfect network, but since I upgraded to the 5G I have been charged double for the 2nd month in a row. The first month they said I didn't cancel my 4G package (why would I want 2 packages) and after cancelling my subscription I STILL got charged double. This is starting to feel like a **** because the service consultants all have connection problems when I tell them my query. When they do finally call, they say I should settle the bill before they can do anything. When I cancelled I was promised that everything is normal now. I am in a loop where I'm being over charged and I'd like it to stop. I have never had issues with rain until I upgraded to the 5G. I need this problem fixed ASAP please.