Here are some useful iPhone codes
You need to press call after entering each code
##5005*86# Erases the Voice Mail number
*#5005*86# Displays the Voice Mail number
*#61# also Displays voicemail number
*5005*86*443# Sets the voicemail number to 443
*#06# Display IMEI number
*#30# Caller-ID display check (on / off)
*#43# Check if call waiting is activated
*#21# Displays any call forwarding settings enabled
*#33# Displays call barring settings
*004# Enable voicemail
#004# Disable voicemail
