Yealink SIP-T3 Administrator's Manual page 359

Default 1
Parameter features.linekey_call_with_default_account
It enables or disables the phone to switch the default account when pressing the line key to dial.
Description
For example, the account on line 2 is not the default account, if this feature is enabled, when pressing
the line key 2 to dial, the default account will switch to the account on line 2.
Permitted
0-Disabled
1-Enabled
Values
Default 0
Supported
All phones except T30P, T30, T19(P) E2, CP920, CP925 and CP935W
Devices
<y0000000000xx>.cfg
Account Settings
353