Hi all, maybe I'm mistaken, but what if just not to use the "C" option of the "topology_hiding()" [1] function? If it is optional - to encode the callid header - maybe you can skip this, and the problem will be solved? [1] https://opensips.org/docs/modules/3.5.x/topology_hiding.html#func_topology_hiding -- best regards, Alexey https://alexeyka.zantsev.com/