4039 with Headset, no "DECT On Modus"

[Tarkil]

Hi everyone!

We are currently upgrading our desk phones, as we want to offer headsets for most of our colleagues. Also we have invited Microsoft Lync. We want to use the Plantronics Savi 740-M headset. For testing we have set up two test configurations:

1) Alcatel Advanced reflexes with a Plantronics HL10 earphone lifter -> good results, but a mechanical lifter is not very pleasant
2) Alcatel 4039 with a APA23 cable

The second is our preferred solution. Unfortunately the headset now is permanently “on”, resulting in a very annoying noise in the earphone of the headset. We did not have this problem with the Advanced reflexes phone. Also the status of Lync is updated to "busy" the moment we take the headset out of it's docking station, even when not having a call. This error is corrected after the first call.

I’ve contacted plantronics support, and they claimed it would be a problem with the 4039 not supporting “DECT On Modus”, whatever that means...
Only solution would be to switch to the 8-Series (and only those with a “EE” ending and newest firmware).

As our system is not supporting IP-phones this is no solution for us, to be exact: we don't have the licenses and the infrastructure.

Question:
Is there a solution for the 4039 phones to prevent the permanent noise in the headset?

Thank's in advance for your answers!