Low intercom tone volume

[haukzinn]

I have upgraded an old telephone system and in the new system, I am using Yealink T21P E2 and T40G phones. The old system made three loud beeps when someone called using intercom. The Yealink phones play almost an inaudible tone when calling using intercom. Is there a way to change the behavior of the intercom alert tone? I have found many posts about the same issue but no fix. Ideally, I would like to change the volume and tone.
I am using 3CX.

Thanks in advance