When I try to use the call log on the phone to dial out it inserts the + symbol because that was the way it was received. Therefore the call fails. Any ideas on how to strip the + sign away before sending the call to the trunk? I tried using + as the prepend and that worked for awhile but no longer.
It would probably be best to fix it at source on the inbound context (use the [from-pstn-e164-us] if appropriate rewrite it to suit if you are not NANP)
In the interim, you could use a [macro-dialout-trunk-predial-hook] as documented in /etc/asterisk/extensions.conf to modify the number dialled