Sprint has its own set of Domain Servers. If you are having connection problems you can try some of these numbers and see if it improves anything for you. If you observe no change then just let the modem select them automatically. The list:

You can enter these by right clicking your network icon in the task bar and selecting "
Open Network connections".
Then right-click the modem listed under "
Dial-up" and select "
Properties"

click the
Networking tab:

highlight
Internet Protocol (TCP/IP) and select
Properties:

select
Use the following DNS server addresses:

enter a primary and secondary (if available) DNS from the above list and click
OK