JUMP! trade-in and bill credits.

Hey Momon, short answer is you'll loose those credits for the 12PM if you're going to receive new credits towards the 14 you ordered. These credits are called "RDC's" reoccurring device credits, and only 1 RDC is allowed per line. I work in a retail location for TMobile and I recommend stopping into your local CORPORATE location to do an account audit to fully understand your current promotion and how it can potentially impact future upgrades. 
 

Regarding your EIP contract and missing order confirmation, I preordered my phone yesterday as well with a similar experience. I'd say that your EIP contact is your confirmation of the order for the time being. But again, your local CORPORATE location will be the final authority with any questions you may have.