Disconnection problem

Hi everyone! I'm having an issue, since I started playing this game, that makes me disconnect (not every time but often) and it happens when:
1) I enter with my character in the server;
2) Use AH of every city;
3) When I enter a dungeon or raid.

I think it's not an internet problem, because I tried a different internet connection and monitored my ping. I tried to clean my INTERFACES (I erased addon) and the WTF folder; I even tried to download different clients, but nothing changed. When it happens no error messages appears, I just see other players walking still on their places. After it happens I must relog 3 to 5 times in order to play, but even after that this issue keeps going... Can someone help me please? I'm sick of this

UP! Please, help me resolve this game pls. I understood it's not an internet problem: When this happens i can still send messages (and people can read it) but I can't. This is happening in ToC and ICC (on every boss fight). This is really annoying because i can't play tank, of course, and healers too. I beg you, help me