Issues with a Cisco Catalyst 2950 switch

Having issues running voice over a Cisco 2950 switch. We have set the switch up to run voice and data, but cannot get the IP phones to work, but the data side is fine, including an AP that is connected to the switch. We have set interface 24 for trunking mode, still cannot do seem to get the phones to work. We are thinking it's an issue with the encapulation command, but cannot find an encapsulation command that would address it for the 2950. We have 3 3560 series switches on the network and they are working fine, voice QoS is great, but this problem is really killing me now. HELP!!!!!