No deadlock letter after being mis sold an upgrade

In April Virgin Media called to offer an upgrade, ever since bb has been dreadful and they told me it would not cost any more than I was paying but would provide a better service if I changed my mobile Sim provider to O2.  They are now charging me £80 a month as opposed to the original £34 per month and the service is poor, i have logged numerous complaints, via phone, via chat bot and via mail and yet to receive a deadlock letter since logging in May which is preventing me taking the issue to OfCom.  I am currently looking after my father in pallative care and have lost count of the hours spent chasing a response to no avail and as you can imagine my stress levels are being tested more than i would like at this difficult time.  How can I take the issue to Ofcom without a deadlock letter or resolution from Virgin - despite them agreeing I had been missold to in May 25 and now just trying to sell me another package. I have been with VM for 12 and never experienced such poor customer services and poor BB speed only to be charged £46pm extra plus additional charges. The complaints process is not fit for purpose and the misselling is likely to be affecting more customers