Logon Extension with phone apps

Hi, Id like to default the username/password inout to numbers only when logging in. It used to default to numbers but now seems to be numbers and letters. Pain for when users try to log in and have 2 of the same numbers toegther in the ext number.
Im sure it must be a endpoint config but not a scooby where to look. Using user managment to auth users

running:
PBX Version:
16.0.40.8
PBX Distro:
12.7.8-2306-1.sng7
Asterisk Version:
16.30.0
Endpoints: Sangoma 406 have the issues.

any advice?