Help HTC M8 compatible with Samsung gear S2 Classic

[greenjeans3]

Is anyone using this combination, the problem I am having is with the message app it is missing from the apps menu. The watch is running on an HTC one m8 from T mobile, but was switched to ATT service. The phone is running android 5.o.1. I then installed watch on Samsung Galaxy S4 and the Message app was there. This app is the one which sets next to the phone app. Would like to know if anyone else is having this problem. Help

Thanks
Jerry