From Bitrefill FAQ:

Where do they work?
Some vouchers work worldwide, some are region-specific, some are country-specific, some are currency specific. You should always check the issuing business website and terms before purchase. If you are not sure if a voucher works in your area, contact customer service.

Is there a buy limit?
Yes, there are daily limits, depending on the product category. Some limits can be increased upon verification of the user account.


Add on top of that the discount of 0% and you will get: utterly uselless service for most of the planet.