Wonder how to capture book end trace

Hello all, I am new to wireshark. I work for a telco company where we had call quality issues on one of our customer location. I have been asked to capture book end sniffer trace between two phones having the issue. So I am really confused on how to proceed that. basically my understanding is that we need two mirrored ports for each of the phone and we need two laptops with wireshark and plug each laptop to the mirrored port and just run wireshark on two pc's when both ends of the phone started speaking?I really appreciate if somebody can help.