voice mail question

I looked around here and maybe missed it but here is my problem.....

....when i recieve a voice mail it usually goes into the phone so i can determine what message i want to listen to. this is what i loved about the instinct ( about the only think i loved about it). But once in a while my voice mail will go into the sprint account. Meaning I have to go to my voice mail account, press my pass numbers and listen to the voice mails one at a time in order and press the number to save or delete.....like back in the day. Im thinking this only happens when I miss calls from a land line but not 100% sure. I called sprint tech but that lasted about 10 minutes when I could barely understand the guy. Those tech have noooooo clue. Dont even know why I bothered. Like I said, this only happens once in a while but its annoying. Thanks for any help and sorry if this has been discussed before.

ok...thanks. i just hope it doesnt get worse.