Is there such thing as a straight perm?

I work in a hairdressers suppliers, i know that there is such thing as a straight perm, which is normally used to relax a curly perm, but i think it is also used to straighten slightly wavy hair. You should be able to still tong your hair to give it a curl without it staying curly. Consult a hairdresser near you, as i think it could be costly.