Yes, you can pay for service before the expiration date. In fact, it is preferred to pay ahead of time in order to avoid the $35 reactivation fee.
When paying for the subscription ahead of time you will not lose any of the time on your current service, if you purchase the same level of service..
- Ex. If your basic service plan is set to expire on 5/15/2015. You purchase a 1 year basic plan on 5/3/15. The 1 year of service will stack on top of the current service plan making the new expiration 5/15/2016.
However, if you upgrade from the basic service to the premium service you will lose the remaining time left on your service plan.
- Ex. If your basic service plan is set to expire on 5/15/2015. You purchase a 1 year premium plan on 5/3/15. The 1 year of premium service will start right then and will expire 5/3/16. In this case you will lose the rest of the basic service plan that was on the unit.