Ting users on the Sprint network will find they do not have a voicemail option, but you have an alternative: YouMail.
1) Go to the YouMail website and register there.
2) Download the YouMail app to your phone. Follow their directions **EXCEPT** for the part where they start telling you to dial in certain character strings to forward the phone.
3) On the YouMail website, find your phone and locate the number you call will be forwarded to. Copy that number.
4) Go to the Ting website and edit the entries for your phone to allow for call forwarding. Paste in the number from step #3.
You're done!! Notes:
a) Everything may not show up at once; be patient if the registered phone doesn't immediately appear on your YouMail account
b) YouMail has a test to make sure everything is working properly, but the test doesn't appear to work with the Ting/Sprint relationship. Ignore their automated test and instead call your phone from another one to see what actually happens.