You can configure the SBC to remove the verstat parameter from SIP messages sent from the system to the calling side. You enable this behavior using the stop-adding-verstat-towards-caller parameter within the sti-config.

The default SBC behavior is to add the verstat parameter to responses sent out to both the UAC (calling side) and the UAS (called side) of applicable calls. This feature keeps the verstat out of messages sent to the calling side. When configured, the system does not add verstat to all 18x and 200 responses to the INVITE towards the calling side, and all in-dialog requests towards the calling party.