Hair spa advice

I have very damage frizzy and thin hair , i have my last year farewell on 29th of april , i was thinking to do hair spa but i m scared of its side effect like if it cause more hairfall or something

Can you guys please suggest which hair spa is best and how i can explore and trust salon in my region , like it should be affordable too

Please help

And as per event when i should to it

Or is there any other treatment i can opt for