Last 4 of sim showing up as phone number

Recently had my damaged iPhone 5 replaced. Shortly after the new phone (and new sim card) was activated, I received a notification saying a carrier network update was applied. After that notification the "My Number" in the phone changes to a series of zeros ending in the last 4 of the sim card. I've had the phone and sim replaced twice now at the Apple Store, and Sprint Customer care has tried everything they can think of on their end. I've tried erasing the phone, reseting it, reseting the network, not restoring backups, starting it as a new iPhone and nothing can seem to get "My Number" back to my actual number. The phone still shows that I have service, and I can still use data (apps, email, imessage all work), but I can't access my voicemail, or make or receive calls or sms texts.