ghost calls to cid:XXXXX

[bfcoi974]

Hello everyone,

After several researchs, I'm really stucked with my issue.
Here is my situation :
I have some T42U phones, which replaces older cisco phones.
Once the phone is installed, this one started making some random calls to a strange format : cid:XXXXXXXX with error on screen (failed to call).
First it makes calls every random times (cf : histo1.png)
So after delete the extension in the pbx, upgrade firmware on phone then apply options for ghost call both in cgf file, the phone makes calls every 50 minutes. (cf : histo2.png)
This behaviour makes users confused because they think they are giving or receiving calls but they phone don't ring.
Thanks for your help.