You can also customize you tariff. The steps on website are easy to follow. You click on “sestavit” (Yes, even on the English page) and choose friends, calls, SMS, Internet. Testing it myself, it would seem it is cheaper to just choose a package because it will be cheaper than a plan which has the same features selected separately. For example, the 1065 CZK plan costs 1485 CZK per month when you choose the same features. You get 10% discount if you arrange your tariff on-line. Unused credit can be transferred but only once. If you do not use the credit it will not be carried to the subsequent months.