I bought the flat I live in three and a half years ago. In practice my flat is one floor of a 3-floor house on a busy street which means the managing agent is more or less responsible for the shared bits. At the time of the purchase, my solicitor looked at who would be the managing agent and said in an ominous voice: 'They are the worst ever.' She was proved right a couple of times since then. I'll pass over the fact that they did nothing to repair the front yard's wall when someone accidentally crashed his Porsche 911 into it (an expensive second of inattention) and that all communication seemed to be limited to asking for the payment of services charges, none of which has ever been visibly invested in improving or even repairing the property.
So when I received a letter telling me I was late in paying my service charges and that I owed them two months worth of it, I was only mildly surprised. I did check that I had a direct debit set up so that they could just debit the amount straight from my account. Then I had a realisation: my managing agent has changed! This is probably why they can't debit my account. you'd think they'd have warned me or sent me a new direct debit form, would you? Well, no. I can't find any trace of any letter of that sort. Mind you, the postman might have mis-delivered it, it's happened before. But still, the old managing agent had all my details, including my mobile phone number so maybe they could have passed this on? Obviously that was way too complicated to do. Nevermind, that's all part of the fun of owning your own flat I suppose.