I agree with contacting your DNO.
Have you identified them yet?
They own the distribution network of cables delivering electricity to your house, but they are not the "retailer" that is (should be) an electricity supply company who sends (should send) you bills.
However
Don't phone them.
The "customer service centre" is pretty sure to be a call centre of low-paid people with a script.
Instead, write a short letter, with your full address and postcode and, if you can see it, photographs of the serial number of your electricity meter and any tags or labels nearby.
Say that you recently moved in and do not know the supplier or the Meterpoint. It's not your fault that you don't know; but if the DNO doesn't know, it is their fault and it is their problem.
A letter has quite a fair chance of being logged and passed along until it reaches somebody who knows what to do.
Don't tell them your phone number or your email address, because you want a written reply. Request this. Keep the letter very short. Don't go on about how long it's taken or how nobody has helped.
Now that your have identified your DNO and sent them a letter, you can, if necessary, write to OFGEM if the DNO doesn't reply in reasonable time or, having replied, does not deal with the problem.