Delay hearing voice in outgoing calls

Hello everybody, I searched the forums but I can’t get a solution (cause it seems nobody has this problem).
When I make an outgoing call and the called party answers, I cannot hear them for almost 1 second. This is really annoying cause I always miss the “Hallo” the other person says.
The called person hears only silence, then he can distinctly hear the noise of the microphone “being opened”, I don’t know how to explain otherwise.
I have various types of SIP phones but the problem happens with all of them.

My trunks are ISDN (BRI) and I use freepbx installed in a pika warp appliance.

I got no problem at all with incoming calls…

Can somebody please help me? I already use “t” instead of “tr” in the dialing options.

What version of FreePbx, Asterisk, & DAHDI are you using?

My guess is that you are experiencing this on outgoing calls over a SIP trunk? If I am right, it is your provider at fault, open a ticket with them.

@depster :
These are my version. There is no DAHDI on Pika Appliance. I’m writing here cause I’m getting no support from the vendor…

freepbx Core
FreeFBX Feature Code Admin
FreePBX Framework
FreePBX System Dashboard

Asterisk version
asterisk-addons version 1.4.8

@lgaetz: no, I have two digital (ISDN) landlines (is the name correct?), not SIP.

Do you have a firewall? Have you changed any of the default SIP signalling or RTP ports? Have you tried an alternative provider?