I'm having an issue with dtmf on 5420 phones, specifically, the number 3. Customer dials a conference bridge toll free number, enters the PIN, and it recognizes every number but the 3. I try using the regular number (non toll free) and it works fine. I thought the issue was on the conference toll free number, however, when I try to dial from a 9508 on the same system, both the toll free and non toll free work great. My thought is that there is something on the 5420 that's causing the issue. I've played with AGC to no avail. Anyone else have this issue or resolution?