An anonymous reader writes: Citigroup has a trademark on "THANKYOU" and is currently using it to sue ATT for using "Thanks." Ars Technica reports: "Who knew? Banking giant Citigroup has trademarked 'THANKYOU' and is now suing technology giant ATT for how it says thanks to its own loyal customers. This is 'unlawful conduct' amounting to wanton trademark infringement, Citigroup claims in its federal lawsuit." Citigroup doesn't appear to be gracious in its branding: Despite actual knowledge of Citigroup's substantial use of and exclusive rights in the THANKYOU Marks, Citigroup's use of the marks in connection with ATT co-branded credit cards, and Citigroup's concerns regarding ATT's proposed trademarks, ATT launched a customer loyalty program under the trademarks "thanks" and "ATT thanks" on or about June 2, 2016. ATT's use of the "thanks" and "ATT thanks" trademarks is likely to cause consumer confusion and constitutes trademark infringement, false designation of origin, and unfair competition in violation of Citigroup's rights. Citigroup therefore seeks to enjoin ATT's infringing conduct and to recover damages based on the injury ATT's conduct has caused to Citigroup as well as ATT's unjust enrichment. In April, ATT applied to trademark "ATT THANKS." Citigroup wants that trademark to be rejected because it thinks that proposed trademark is "confusingly similar to Citigroup's "THANKYOU Marks," according to its lawsuit.