If there are errors in the notification letter, you can object to the price increase in writing and insist on continued delivery at the old prices. Make sure you use the right wording and state explicitly that you object to the price increase and why. It is also important to mention that you do not want to cancel the tariff so that there are no misunderstandings with the supplier.
In the case of non-transparent price increases, you can seek advice from the consumer advice center in your federal state. In addition, it is also a good idea to inform the Federal Network Agency. Nevertheless, it is advisable to pay the increased prices first and possibly have them reimbursed later. Don’t just stop paying because you feel right.
Price guarantees are also a controversial topic at the moment. Despite agreed fixed prices for electricity and gas, the providers ExtraEnergie and ExtraGrün, for example, wanted to increase prices. A decision by the District Court of Düsseldorf prohibits this in these cases.
So don’t just check the letters about the price increase for formal errors, but also pay attention to possible price guarantees in your supply contract. Under certain circumstances, they can rule out a price increase. It is important to note that the exact wording and possible exceptions are important.