We have headphones but are unable to answer calls, unless it's a direct call using F66+# extention. If we only type the extention numbers, the headphone does not ring and if I'm not besinde my telephone, I cannot answer the call. Our phone are M7310 from Nortel. Plantronics suggested a HandLifter but anyway, it doesn't work. We probably have to set up the phone somewhere to be able to answers call with the head set.