I work at a service center for Sprint, and used to work in the local mall doing Sales, and it's true...You call up cust care/tech support, there is a high chance you will get someone who has no idea what they are doing. if it doesn't work out right, hang up, call back again...I had to do this 5-6 times to get a customer set up with his new phone, and it took about 3 hours, but he was happy.
Anywho, concerning this visual voicemail... The second tech i spoke to said unfortunately they disabled the option for them to change the voicemail number, even for their own accounts, as he was trying to do the same thing...They did this about a month to a month and a half ago. He said it was due to some one bouncing signals off towers for other countries, i think... But he also mentioned the one he was looking at using was from
www.vodavi.com and it had a built-in windows mobile client. Just wanted to throw this out there...
(Also, I am currently severely sleep deprived, but couldn't go to bed until i spoke to at least 2 technicians.)
Peace.