I want to use two ad networks in my app

Hello friends I want to use two ad Networks in one app I want to call admob ads when facebook ads failed to load is this correct way to call ads

You can use two ad network at the same time . But the use case you’re tring to implement might affect user experience.

Is it effect to my ad network account?

No. Will not affect your publisher account as Google support using mediation program for publishers to increase their earning.