thanks i thought so. But it doesn't work this way, at least when i tried it last time. There might be something wrong with the phone. Never mind thanks
The part before 420 may differ. Most usually it is 00, but maybe you have to dial some number to get to outer line, or the international calls are blocked... Just find out how to make international calls (ask the owner of the phone, or the phone company), then dial 420 for Czech republic, and then the nine digit Czech number (that remindes me - all Czech phones have been renumbered a year or so ago, make sure you use the up-to-date number. All Czech numbers now have exactly nine digits and no leading 0).
international prefix, 3 numbers 011 Country code, 3 numbers 420 number, 9 numbers xxxxxxxxx input them in that order and you should be good to go, this works from Canada to Czech no problem.