I need help. am new to asterisk dialplan. when i call a number from my softphone with the + prefix character in front of the number the call wont go through i have tried all i could to in my extension file but to no success.
- is not a valid part of the calling number in fixed telephony. It is only valid in mobile telephony. You can use 00 instead of +.
If you want us to help you, provide some debugs. Asterisk console output would be a good place to start 
Just in your dialplan add the following:
exten => _[+].,1,NoOP(International)
same => n,Dial(SIP/${EXTEN:1}@your_trunk)
This should allow you to handle calls that start with the +.
Success.
You didn’t add the 00!
Yep, didn’t add the leading zero’s.
But my experience is that most sip trunk providers do not want the leading zero’s.