Regular Ppruners will know that I think there are several points of contention in our terms of service and pensions arrangements, but this isn't one of them.
Look at what you are saying. You made a long term committment purely for the attraction of a very short term carrot. You then reneged on that committment at the very first "better" opportunity that came along. How committed were you?
The bottom line is that the rules of the sytem were properly applied in your case. You have no reasonable case to ask for recompense. The Service applied the appropriate penalty clause for your having sought very early release from your extended committment. If you try to argue otherwise, I fear you will be the one "taken to the cleaners".
Regards
Ginseng