Your phone is already "locked" in that it will only work with service through
Verizon, and there does not appear to be any easy way to unlock it, that is,
make it so it will work with other services.
As well, even if you could get it unlocked, it does not look like it would be
possible to get it to work with most any other service.
Not only that, but if you are looking to go the prepaid route, and if you
could unlock your phone, and get it work with another service, it appears it
would be very hard, if at all, to get a prepaid card for it.
When your service with Verizon ends, your best bet within the prepaid realm
is to ask around and see what prepaid phones and services work best in your
rural area. Ask any friends that use prepaid services what service they use,
as well as asking any local cellphone dealers what they would suggest.
If TracFone is an option in your location, it could be easy and relatively
inexpensive to try them out, as they have a deal where you can get two 60
minute prepaid cards and a refurbished Nokia 1100 for $19.99.
You can look at what they offer at their website.
If you use your cell phone quite a bit, the prepaid route might not be the
best way to go. You need to look at your usage and the fact that prepaid
cards expire with time, and that prepaid "per minute" charges can be pricier
than traditional plans.
If you need any clarification, please feel free to ask.
Google search on: unlock OR unlocking "CDM-8600" OR cdm8600 OR 8600
Looking Forward, denco-ga - Google Answers Researcher