Problem with calls randomly ringing back to a set

[animasola]

I get a call from a customer. They say they get "phantom calls" that ring on one set. It doesn't happen a lot. Just enough to be annoying. Also if there not in, the calls fill up there v-mail with disconnect messages. I sent a tech on-site. He said he fixed it by changing the operator status to a different phone. I just got another call saying it was still happening. Any ideas?
Thanks in advance!

 

[lugerlover]

drt to prime on a few trunks may be wrong

 

[norstarboy125]

do they have analog or digital trunks... what type of system what rel. sft.? need more info

 

[animasola]

Analog trunks, MICS,not sure of the release. At least 4.1. It's only about a year old i think.

 

[hawks]

Make sure that you have Disconnect Supervision on the Lines.