Continuously being overcharged

I have been a virgin customer for a while now, I had noticed my bill had increased by almost double to £170 per month & couldn't simply afford to pay this anymore, so on the 13th April I called to cancel my package & was talked out of doing so instead I decided to just continue with broadband only for £39 per month. Virgin have continued to take £170 per month from my account despite sending me my new contract of £39 for broadband only via email. I called up on 12th June to explain they had been charging me incorrectly & received no help whatsoever from the person on the other end of the phone call, I asked for a refund of the difference of what I had been charged & was told this wasn't possible as virgin do not do refunds & if I wanted my money back that I needed to call my bank & request a refund via them. The bank were extremely helpful unlike virgin & refunded me my money immediately thank god as I was in a situation that wasn't going to mean I could afford to pay my rent as virgin had been stealing my money (I have an email confirming £39 per month new contract/package dated 13th April) I have since been sent an email from virgin letting me know my new bill is ready & the amount owing is £351.50 & my package is still showing as £170. I am now extremely upset & not getting anywhere with this company who are not updating the system to my new contract amount & keep taking my money  that does not belong to them. No one on the phone seems to be able to resolve my situation, I cannot afford to pay this amount & really don't know what to do, This is causing me extreme stress & its causing other bills not to be paid & I do not want to get in debt for virgins mistakes. help!