Oh, by the way, I'm pretty sure mistell isn't an actual English word. you can use "mistakenly say".
Also (Corrections are in brackets):
"(To) prevent this accident, you can (use) Alex as (a) code name (for サイモン). In addition, you can (use) enemies names or plans in order to prevent those (mistakes). Code names can tighten the (bond?).
P.S: is there instructions for the buttons in the message box? I don't understand ; ; What is the 3000/1000 pt?? Thank you > <
(61) Puchny 2013/02/17(Sun) 14時頃