I don't know exactly how Let's Encrypt handles this situation. Usually people are inadvertantly caught by the domain name filter ("Master Card, Bucharest's oldest greeting card and gift shop..."); they don't actually represent the billion dollar company in question...
This came up about a month ago with another company:
The company and Let's Encrypt discussed it, but i don't know what the final result was.
You may be able to work something out, but it will probably take a little time.
@cpu: Ping. @bootika is looking for a certificate for a Mastercard domain.
@ahaw021 If no CA ever issued certificates for prominent organizations, those organizations wouldn't be using certificates right now. It just requires more red tape, and maybe some CAs won't do it at all.