@SuperMario I've been unable to replicate the FPS drops you're describing. Some troubleshooting and questions for you:
Do you experience the same FPS drops when playing offline/against bots?
Is it the same when playing over your cellular network and your home Wi-Fi?
Have you set up a scenario profile for Call of Duty in Armoury Crate?
You can also check if these steps improve your situation:
Clear cache files sytem-wide (Settings -> Advanced Mobile manager -> Cleanup)
Uninstall and reinstall Call of Duty