Post Office Motorcycle Insurance

after 3yrs of paying around £90 underwritten by KGM they made it £425 because they say KGM can no longer cover this bike.so they offered me a different company.i declinde and went elsewhere and got it for £151 UNDERWRITTEN BY GUESS WHO ....KGM.i told the post office which answered with Devitt or Thebikeinsurer that KGM say they did not know how to work the system.in this case year of manufacture rather than date of first reg.in this case an RC30 made in 86 but reg in 2014