Change the number of rings - Samsung D500
This is a network related setting. Do the following.
from your home screen, type "* 61 * (voice mail access
number) ** (time in multiples of 5 ) #" and then press SEND. For
example, if my voicemail
access number is 404-555-1212 and I want it to ring for 20 seconds
before forwarding to
voicemail, I would type: *61*14045551212**20#