Thanks for your quichly reply.
Basically they are using 3 types of these wireless IP Phones:
Unidata WPU7700, WPU788, ICW1000G
Since it is getting quite urgent we should check whether prioritizing the SSID or Voice traffic is a possibility or not. In the meantime we are also checking with the supporter of the phones if enabling WMM is an option or not.
I would like to supply to my customer all the options.
Thanks in advance for your support.