This is a problem I encounter every time that I buy a bike here in Philippines.............................
Pinoy mechanics LOVE to
graunch down bolts so that mere mortals can no longer remove 'em.................best is to give the part a few days of WD-40 (just to show that you mean business!), then take a cold chisel and try to bash at the fixing
radially until it starts to move. Attack the bolt alternatively at "12 o'clock" then "6 o'clock" until you notice some movement. If the fixing has a head, this SHOULD get it to move. I ALWAYS use a cold chisel for such problems, and NEVER an impact driver..........................