Analog phones connected to RTP300 drops digit from dialed number

I’ve been checking this out all day. I have 4 phones out of 15 that drop the number 3 when ever they dial any phone number. At first I thought it was Asterisk wasn’t able to dial the number because the error always stated number cannot be completed as dialed. I was getting this message for calls to their won extensions which all had the number 3 in the extension i.e. 931, 932, 933, etc.

After checking the log, I discovered that it dialed 91, 92, 9, etc. When I replaced the phone with my own analog phone which isn’t the same model, it worked fine. Now my question is, is there an adjustment that would allow the missing number to register on Asterisk.

Asterisk Ver 1.8.11, FreePBX 2.10.0.7, RTP300 version 3.1.24

Any information to point me in the right direction. I will probably just replace the phones, but these are brand new phones and they worked on and off for the first few days.