I'm on ATT and only txt/pic txt within the US. 1) If I download one of these JB txt msging apps, can I cancel my $30/month txt MSG plan? 2) any additional in-app or per-txt-msg cost for using these apps? 3) any reliability issues? 4) which app would be the best one to use? 5) other then losing my unlimited mobile to mobile plan, when I cancel the AT&T txt plan are there any other draw backs I should be aware of? Thank you for your input!