OMG i was wrong, i did pay too much

When i checked the DVLA site before, i was looking at cars registered before 2001, where the tax goes on engine size. I didnt look at cars registered after that time which means mine is classified on emissions. I checked those, and my form was correct, i should have paid £79, not the £101 that the post office charged me

I will be on the phone to the DVLA tomorrow