By default, the SPA525G marks its voice traffic with a COS 3 marking (should be COS 5). It is the switch's duty to prioritize the marked traffic accordingly. If the switch or router that the phone is connected to does not accept or discards the marked traffic, the voice packets will be treated just like data packets. You might be experiencing choppy or loss of audio because there is high bandwidth usage which starves out the voice traffic. If you don't think it's a bandwidth issue, you can try upgrading the firmware on the phone.
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...