[ScrapMaker]

You can call Sprint and have them statically change your voicemail setup. You can specify a third-party voicemail provider, like callwave, or in this case, TrapCall.

Normally it rings to Sprint's voicemail service, but you can most definitely have it changed, and at no cost. There are tons of threads on it, and I forget the specific term you have to ask for, but there is some phrase you can use when talking with a CSR on Sprint, to get the swap made for free.

Just keep verifying that you won't have to pay. Also, make sure that whatever it is that you want to switch to is really good enough, because I don't know how keen they are on switching back and forth.