My office has 2 RCA 4-line intercom speakerphones (Model 25423) that were just purchased about 2 months ago. So far everything works fine except for the intercom. We can't figure out how to work them between the two different phones. I have looked through the manual and even called RCAs customer service line but we still haven't figured it out. They told me what to push but a call had to be on the phone for it to work so I couldn't test it out with them on the phone... Help! This is so frustrating.