What do you want us to do? Magically reset your AD username/password on your companies domain?
try resetting your password to something you KNOW is right
make sure the username you enter is correct
make sure you are entering the correct domain
make sure caps lock isnt on
type really slow so you don't make any mistakes
are you even entering a domain name into your dial-up connection? Right click your dial-up connection > Properties > Options. Under Dialing options there should be a check box for "Include Windows logon domain". If its not checked, check it and enter your domain. If its already checked and your 100% positive you have been entering the correct domain name, uncheck the box.
If all that fails, contact "support" again.