Hi Mel409,
We're glad you've reached out to us about VoLTE on your iPhone 7. We're happy to help!
We can confirm that iPhone 7 is compatible with VoLTE. Here's a guide with detailed technical specifications:
iPhone 7 - Technical Specifications
As the availability of VoLTE is determined by your wireless carrier, we also want to mention that the following article indicates "At Sprint Wireless, VoLTE is available only on iPhone 8 and 8 Plus or later":
Wireless carrier support and features for iPhone in the United States and Canada
We're here for you if you've got any questions!
Have a great day!