I am extremely disappointed with how OVO Energy has handled my account and billing. I joined OVO on a **fixed-rate tariff starting in December 2024**, after comparing prices with other energy suppliers. All providers were offering similar rates — I only chose OVO because my **letting agency required me to start with them**. Otherwise, I would never have signed up. Recently, OVO sent me a notice claiming they had “underestimated” my energy use and recalculated my bills (!), showing a **negative balance of over £500**, even though I am on a **fixed tariff** where the monthly amount was identical every month for last 9 months. This makes absolutely no sense, as the whole point of a fixed tariff is that the cost remains consistent based on usage. To make things worse, the **account number quoted in their correspondence doesn’t even match my account**, which makes me believe they may have **wrongly applied a previous tenant’s outstanding bill to my account**. This seems to be a **serious internal billing error**. This has caused unnecessary stress, wasted time, and uncertainty. If this is not corrected promptly, I will be escalating the matter to the **Energy Ombudsman** and seeking compensation for the inconvenience, time, and legal costs this situation has caused. I strongly advise anyone considering OVO Energy to think carefully — their billing system and customer service have left me with **zero confidence** in their ability to manage customer accounts fairly or accurately.