Can go to ah boy, ask their mechanics to do that...
Last time I make the butt higher 15cm for $20 ('cos they must make
and attach additional metal pieces on the suspension) ... but, if
you make the seat lower, should be cheaper .. $10 maybe can ...
just press release the screw, press the bike, and tight the screw
again...
Is the bike tilted too much? If yes, then it is not safe, must
lower down the seat, especially when squeezing and running at low
speed at traffic jam... it is dangerous if the seat is too high,
you may fall to moving vehicles beside you.