Jambon - try searching on here for "stuck seat post" - definitely worth a read before you give up and definitely worth doing.
I used to arrive soaked in sweat and aching terribly because my seat post was stuck too low for commuting, but thought I had to put up with it.
Having unstuck (actually chemically melted out) my seat post and set to the right height, commuting is an absolute joy, I am far more confident a rider because I have energy in reserve and life is bliss!
If your frame is steel and your seat post is alloy, then it is a cinche to melt it out, but PM me for more tips if you need. Good Luck!