Maintaining PAYG Slovak SIM card, ID requirement?

[international]

Is there an ID required to buy a Slovak SIM card?

What is he cheapest option to maintain one over the years? Can you top it up online with some minimum amount if needed?

[123456]

Found this in the "guide to mobile services in Slovakia":

If you intend to call more in Slovakia and want to avoid roaming charges, the easiest solution is to buy a prepaid SIM card. For its purchase Slovak legislation requires verification of personal data. Therefore cards are not sold as freely as in some other countries.

Sellers will ask buyers for their passport or identity card if from European Union, or permision for stay in Slovakia, on the basis of which they will verify the buyer’s identity. The minimum age limit for buying a SIM card is 15.