Getting callcentric error message when asterisk is still


i’m having an issue with intermittent error messages from my service provider callcentric. The calls will go through with no problem then at random intervals i you will get the callcentric error message. I have a forward set for when the pbx becomes unregistered but it keeps the registration. I noticed in the error log i’m getting entries like

NOTICE[2943] chan_sip.c: Call from ‘’ to extension ‘s’ rejected because extension not found.

can anyone help, this is a very high priority

restarting asterisk corrects this problem but it still comes back.