How do you say ‘yun na!’ in English?

You will use ‘have it’

The New Lexicon Webster’s Encyclopedic Dictionary’s usage of ‘have’: To assert, insist on

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talaga!

Siya talaga! Paniwalaan ninyo ako.

I have it that it was him! Believe me.      

sinabi na!

Sinabi ko nang pula; makulit ka.

I have it that it should be red; you are persistent.

yun na nga!

Iyon na nga e. Bakit ka pa tanong ng tanong?

I have it so. Why do you keep on asking?

yun na!

O, e di, natalo nga ang Bigwas Team. Iyon na!

So, Bigwas Team indeed got defeated. We have it! (or ‘I have it/that!’ or ‘I/We have it!’)