Go to bunnings and get all the required parts to connect a water tap to the top of your mast.
Take the top bung out of the mast, connect the hose, turn the tap on, bend and bump the mast in multiple directions until it goes POP and your mast is apart.
If it's really stuck then it will be a 2 beer job.
Alternatives include using a towball, a tree and an icicle hitch.
Now go to bunnings and buy some electrical tape, and every time you sail, wrap some tape around the join. This will stop sand getting in and you won't have a stuck mast ever again