Klausner Technologies is suing YouMail and HTC over alleged infringement of its visual voicemail patent, which allows users to read their voicemail messages from handsets and computers.

Klausner alleges that YouMail is using its technology without paying royalties and says HTC’s MyTouch 3G infringes on its visual voicemail patents. Klausner currently has 27 visual voicemail patent licensees under its U.S., European and Asian patents.

Klausner has successfully sued several companies over its visual voicemail patents, including AT&T, Apple, LG Electronics and Google.

The California law firm of Dovel & Luner filed Klausner’s lawsuit in federal court in the Eastern District of Texas.