How to set up an outgoing call?

Question

Asterisk

Hello, tell me how to set up an outgoing call?
The situation is this, there is an Asterisk server in the office, a voice gateway is connected to it from the store via external IP, Grandstream HT813 to which the analog line (FXO, configured as a trunk in the asterisk) of this store and an analog phone (FXS, configured as an extension in the asterisk) are connected , with an incoming call, the call reaches this phone, but the outgoing call does not work, writes chan_sip.c:23273 handle_response_invite: Received response: "Forbidden" from ';tag=as04bb3bdb'