Only 1 line per extension


I currently have 2 lines for each extension, this is a default configuration, I want just 1 line per extension.
How I can do that?

example (actual conf):

phone1 ext 101 is busy in one line.
phone2 ext 102 is available.
in the ring group ext 101 is the first option and ext 102 the second.
incomming call go to the ext 101 line 2.

I want to delete the 2nd lines of all extensions, then the ring group will work like must be.

You probably need to turn off “call waiting” for that extension many hard-phones will accept calls on unused line buttons if it is on, it is however phone specific.