They just seem an incredibly disjointed company with no lines of communication between departments.
We were billed for 2-3 months after switching to BT iirc. They repeatedly denied it and then decided I owed them money! At one point I was receiving several automated calls a day from their debt collection arm, plus letters. This is despite them admitting in writing (twice) that they were in the wrong!
In the end I went through OTELO, who sorted it out but it took 3 months, then a further ~6 for Tiscali to give me the paltry £25 compensation OTELO ordered them to pay (which they were ordered to pay within 28 days).
Make sure everything is in writing and log the details of any phone calls. Personally, next time I’d write to one of the tabloid consumer affairs columnists. At least they seem to be able to get £50 and sort things out quickly!