I just discovered this. For every $100J credit you load on your phone, you get 1 point. Once you have 34? points I forgot, sorry - you can convert them to $100J bonus credit on your phone, with a 30-day expiration.
You can only convert to $100J credit once per month. As it turns out, I have 12 months worth, lol.
The policy (?) also states that this $100J bonus credit can be used to jumpstart your service when arriving (you know how sometimes you have to add credit when you get here, to be able to use the credit you have).
*131# SEND to find out your points
*131*100# SEND to request $100 bonus credit.
Each SEND costs $1j
NOTE! You can also use the accumulated points to buy a new phone at the store. In that case you can use all the points at once.