I believe you need to set it up from the cellphone first. Any other time you can do the following.
You can call your phone number from a landline and when you hear your greeting, press the # symbol to interrupt the greeting. Then follow the prompts.
Well, you only have to do it one time. Do you just use this phone for a voicemail box? I guess I'm asking, Why pay for service on a phone you don't use?
I have a bunch of phones on my account and this is just an extra one that no one has used. It has a contract but only adds $10 per month to the bill.