You guys with Alltell service sometime need additional init line in wvdial.conf as well correct domain and pasword configuration.
PHP Code:
[Dialer Defaults
Stupid Mode on 
Modem 
= /dev/ttyACM0 
Baud 
921600 
Init 
ATZ 
Init2 
ATQ0 V1 E1 S0=&C1 &D2 +FCLASS=
Phone 
#777 
Username = ??????????@alltel.net
Password 
alltel
Init1 
ATZ 
ISDN 

Modem Type 
Analog Modem 
Auto Reconnect 
on 
Carrier Check 
no 
[Dialer shh
Init3 ATM0 
[Dialer pulse
Dial Command ATDP 
I see other people having same problem, if it wont fix it you may want to send them a private message or e-mail to get exact specs.
Those some of posts i seen with this same problem:
http://ubuntuforums.org/showpost.php...1&postcount=53
http://ubuntuforums.org/showpost.php...&postcount=205
I'v never worked with Alltell so i'm somewhat fuzzy on what exactly causes exit code-2 in this case but i know that bunch of people got their Alltell Evdo modems running using this how to .