WMS software is for the Nortel 2300 series wireless controllers. The 2211 is a wireless IP phone OEMd by Spectralink.
What type of wireless infrastructure do you have? There are several settings, each of which are different, depending on what manufacturers wireless infrastructure you have in place.
A couple of things to check are:
Enable SSID broadcast on the SSID the phone attaches to
Set your DTIM interval to 3
Turn off any active scan features on the APs.
Disable auto power and auto channel selection on your APs. Hardcode the channel and power levels.
Those are some recommendations I've come across. If nothing else its a place to start.