Samsung M520 Owner's Manual page 119

Checking for Voicemail Messages While Roaming
When you are roaming off the home network, you may not receive on-
phone notification of new voicemail messages. Callers can still leave
messages, but you will need to periodically check your voicemail for new
messages if you are in a roaming service area for an extended time.
To check your voicemail while roaming:
1.
Dial 1 + area code + your wireless phone number.
2.
Enter your voicemail passcode at the prompt and follow the
voice prompts.
When you return to the home network, voicemail notification will
resume normally.
Section 2D: Controlling Your Roaming Experience 93