Vitajte!
I am sorry, but Slovak version of this site is not yet available. I think, that T99 will be usefull for you (to remove diacritical marks from letters Č Ď Ň Ŕ Š Ť Ž from Slovak alphabet that cause decrease maximal length of sms from 160 to 70), so please read about T99 in one of the following languages:
If you can speak Slovak, please help translate the site to this language - send me an email, I will write you all details in an answer. Thank you.