Link Ticket not available in phone ticket - Agent interface

[res5it]

Hi all... I'm new in OTRS so I need your help guys.
I'm have Admin rw privileges so I'm able to see " Link Ticket" link in new phone ticket. But every body else as agents cannot see this link, the only way I can make them see the link is by adding RW privileges to Admin group ,but this is not acceptable, I don't want Agents to be admins. Can someone help me whit this please ?
I'm using OTRS v 3.0.9, not upgraded to 3.0.10 yet, first I want to resolve this issue.

Thanks in advance