You can simply switch the SIM card from your iPhone 7 to your iPhone 11. This will maintain the same cellular service that you have on your iPhone 7 on your iPhone 11 once you switch the SIM card.
You can even transfer all your data from your iPhone 7 to your iPhone 11. If you are interested, then you transfer the data as follows:
Transfer Data from old iPhone to new-
Do you have a backup created either on iCloud or on your computer?
Method 1 - Backup your old iPhone on your computer like this ➔ How to back up your iPhone, iPad, and iPod touch - Apple Support and then Restore your new iPhone from that backup like this ➔ Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Method 2 - The Quick Start method and here is how to do that ➔ Use Quick Start to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support
Axel F.