Okay, I may the only person on the planet that has made this mistake (twice) but I will share here. When you use your Verzon phone to tether to a PC/Laptop you dial **7284. So if you dial *7284, guess what, you forward your phone to 84 that is not a phone number and any call to your phone will ring busy, no voicemail either. Here is the trick to clear the error so can recieve calls again.

Call Forwarding: dial *72 + the number you wish to forward to. Press "SEND". To deactivate
call forwarding, dial*720 "SEND". Listen for confirmation, then press "END".

Now there may be a pratical application for this error of dialing *7284 or *72XX. Suppose you don't want to be called or be left a voice mail. This will prevent both. However the phone will still dial out.

Other Verizon codes:

Voicemail: dial, *86, then press "SEND". This will take you to your voice mail box. It will ask
for a password, enter 6245 (this is your temporary password until you make a new 4 digit password) there is a voice prompt to guide you through the set up of your mailbox.
Call Waiting: when you here the call waiting tone just press the "SEND" key to toggle back and forth between calls.
3-Way Calling: place your first call as usual, then dial the second number and press "SEND" again. When your second call connects press send again to connect both calls.
Call Forwarding: dial *72 + the number you wish to forward to. Press "SEND". To deactivate
call forwarding, dial*720 "SEND". Listen for confirmation, then press "END".
NO Answer Transfer: dial *68 + the number you wish to forward to, press "SEND", listen for confirmation then press "END". To deactivate dial *680 press "SEND", listen for confirmation then press "END".
Caller ID Blocking: (call by call basis) diva *67, then dial the phone number.