Type of sim card Topup link
Australia https://www.prepaidzero.com/australia-topup.html
Austria https://www.prepaidzero.com/austria-topup.html
Belgium https://www.prepaidzero.com/belgium-topup.html
Canada https://www.prepaidzero.com/canada-topup.html
China (call balance only) https://www.prepaidzero.com/china-topup.html
China (Unicom) http://hk.chinaunicom.com/tp
Denmark https://www.prepaidzero.com/denmark-topup.html
Europe (All of Europe) https://www.prepaidzero.com/euro-topup.html 
For Three Mobile sim cardshttps://portal.prepaidzero.com
(if your sim card was activated from the portal page, please top up from that page by logging in)
Europe (Travelsim) https://www.prepaidzero.com/europe-topup.html
Finland https://www.prepaidzero.com/finland-topup.html
France https://www.prepaidzero.com/france-topup.html
Germany https://www.prepaidzero.com/germany-topup.html
Greece https://www.prepaidzero.com/greece-topup.html
Hong Kong https://www.prepaidzero.com/hongkong-topup.html
Indonesia https://www.prepaidzero.com/indonesia-topup.html
Ireland https://www.prepaidzero.com/ireland-topup.html
Israel https://www.prepaidzero.com/israel-topup.html
Italy https://www.prepaidzero.com/italy-topup.html
Latin America https://www.prepaidzero.com/latin-topup.html
Netherlands https://www.prepaidzero.com/netherlands-topup.html
New-Zealand https://www.prepaidzero.com/nz-topup.html
Norway https://www.prepaidzero.com/norway-topup.html
Portugal https://www.prepaidzero.com/portugal-topup.html
Russia https://www.prepaidzero.com/russia-topup.html
Spain https://www.prepaidzero.com/spain-topup.html
Sweden https://www.prepaidzero.com/sweden-topup.html
Switzerland https://www.prepaidzero.com/swiss-topup.html
United Kingdom https://www.prepaidzero.com/uk-topups.html
United States https://www.prepaidzero.com/usa-topup.html
World https://www.prepaidzero.com/world-topup.html