Virgin Media is not helping

So I have been having intermittent Internet issues for almost 2 months now, and Virgin Media doesn't want to help.

Each time I speak to one of their agents, they don't keep their promises and instead of actually resolving the issue, they send an engineer who either won't turn up because they know they don't have access to the roof or say the same thing "There is no issue in your apartment, the issue is on the roof but IRS (never heard of them) won't grant permission."

I live in a flat and the engineer requires access to the roof to resolve this issue but for some reason Virgin isn't contacting the person in charge.

They randomly close complaints, won't tell me which department actually deals with someone contacting the Council for the roof access.

They constantly lie stating that they did contact the person in charge of roof access (IRS), but the actual person who works for the council says otherwise.

I have requested a deadlock letter but I do not want to continue with that route if it can be helped.

At this point, I am not sure what to do.

Thanks.