Someone else reported this in the bugs section yesterday.

Davey says support has been made aware of the issue.

Yeah, is a known bug it seems.

It is happening to me on Plarium Play and on the iPhone.  

A few clannies have complained also.

since I use clan chat a lot in this  game . Yes  it has  happened to me as well

First time I wrote out a sentence  not aware that as soon as I started  typing it changed the channel on me from clan to global. Hit the send  button only to realize I just told  Global chat my life story ment for  clan mates  :/

Now that I am aware I have caught  it switch channels  on me when I start typing in clan chat a few times  but I see the  channel change then get it back to clan and continue