You can request that phones be allowed to or not allowed to have certain dialing access, including long distance.
By default, VoIP phones are set to allow outbound long-distance dialing to North America. Your department may choose to broaden or limit the phone configuration to restrict outbound calls to local calls or even campus-only calling, or expand it to include international long distance. The lowest level calling restriction is campus only.
Your department may opt to restrict access to long distance by requesting an access code.
Incoming calls to VoIP phones cannot be blocked.