More lines for an extension in AMP

Hi all people!
I had a problem that i’ve solved with a change to exten-vm macro…
When there’s a call to a sip extension, another caller receives busy tone or a voicemail announce (if setted).
That’s not good! Wink
The various extensions that i have are Grandstream GXP2000, with 4 lines…
It’s possible set AMP to assign more lines for each extensions, without modify the macros?
Many thanks!