Here is a useful tip if you always keep on missing phone calls because it takes you too long answer because you’re fumbling in your pockets to get your Blackberry. On some providers you can change the number of rings before your voice mail answers.
Bell Mobility: *94 +(number of rings, ie 5 for 5 rings) and send.
T-Mobile UK: **61*44051(insert your tell number here starting with the 7)**25# – 25 is the highest value.
T-Mobile US: **61*18056377243**XX# – where XX equals time in seconds
Vadofone Australia: **61*011308980*11*nn#