Over charging and not picking up customers phone calls

I’m convinced rain is billing me someone else’s account because I bought the my rain one package for R559 however I was billed R732 for my first month and when I tried to contact them, they never pick up the phone or respond to my queries. I paid the R732 because I needed internet, but this month they’re billing me R1009, and still not picking up their phones. Their service and their internet is absolutely horrible. I’ve only been with them for two months and I’m already fed up.