It should not be 4 digits that are sent out of E1 Interface. It should atleast be office-code+subscriber number, which is typically more than 4 digit. For example in NANP, it is 7 digits. So I have some questions for you:
1) Which country is this deployment in?
2) Is it a local or a long distance call?
3) What number does the user dial?0
Generally, you can change number of digits that gets sent out on the E1 interface on PSTN Connection - S0/SU0-.., Advanced Setting - Outbound call routing
You need to set it to Manual mode, click Edit and edit patterns in the new window that opens up.
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