Yeastar S20 deletes the 4 in the outgoing call

Good morning,
I have a problem that I am not able to solve in any way.
I have a Yeastar S20 switchboard with only one Trunk for outgoing calls.
The problem is that if I try to call a phone number that contains the number 4, the switchboard automatically deletes the number 4 and obviously the phone number called appears to be non-existent.
I have no problem if I call a phone number that does not have 4 inside.
Can you help me?
I upgraded my switchboard to the latest firmware version on


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