Oh daniellesh29, that's rough for sure.
I do have some suggestions for you that can help you out. Are you getting an "insert sim card" error message at all? If so, you'll want to make sure the sim card is placed into the phone properly. You can check out the link below to give you a visual picture if you need it.
You'll also want to make sure you're within T-Mobile's coverage. You can check the coverage in your area using this link: https://www.t-mobile.com/coverage.html
If you have any other devices near you that has the same size sim card slot, test it in that phone to see if you're able to get signal using that phone. This will help us determine if the sim is the reason for this or if this is stemming from the phone. If the other phone does get signal, then a last resort would be to Master Reset your Grand Prime.
If you're not getting signal an either phone, and you are within T-Mobile's coverage, you'll want to Contact Us and speak with Tech Support or message our T-Force team via the Facebook, Twitter, or Google+ links below. You can have either of them reference DOC-7461. It has the next steps they'll be able to take that will help get you connected to the network.