Billing and cant link my e-tag

I just bought a e-tag and tried to link my e-tag to my account,. When I phoned the call center they said because the previous owner had a e-tag I must get proof from my bank that I own the car and then go to one of their centers. But by magic I am still getting the bills for the car, if the e-tag is still registered under someone else name and the car registration number why not send him the bills. Now I have to do all this admin and work just to get a e-tag on my vehicle. They also send me a bill for a car that is not even mine. The registration number is mine according to them but the photo you can clearly see it is a Mercedes Benz with a different registration number. My car was a Kia Picanto - a big difference. When I phoned them I must fill in forms and do e-natis search (which I must pay for) because I do not own the car anymore. Again my problem to sort out for their mistakes. They beg us to get e-tagged and pay them but then you get this service.