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?

The creds for the login phone app (hotdesking) are the user’s primary extension number and their VM PIN. All numeric.

yup, however when logging on to the phone, the sangoma s406 defaults to letters and numbers. so for example if an extension is 700, and the user types it fast, itll type out 7(space) as the zero key is pressed twice in quick sucession.

i want the phone to default to numbers only first