[**Gotcha**] [wiki](http://en.wikipedia.org/wiki/Gotcha)

*Gotcha* and *I gotcha* are relaxed pronunciations of "I['ve] got you", usually referring to an unexpected capture or discovery. Gotcha is a common colloquialism meaning to understand or comprehend.

It is the reduced written form of *got you* = *got* +‎ *-cha*

Gotcha can also be spelled as *gotchya* whereas the related term, *getcha*, is made by joining the verb and pronoun, *get you*, with *-cha*.

There are no *written* instances of "gatcha".

My guess is that the OP has heard the [Blondie](http://www.youtube.com/watch?v=mFerLNdpwO4) song, "One Way or Another" recently covered by the British boy band, *One Direction* and mixed "gotcha" with "getcha". :)

    One way, or another, I’m gonna find ya
    I’m gonna getcha getcha getcha getcha
    One way, or another, I’m gonna win ya
    I’m gonna getcha getcha getcha getcha
    
    One way or another, I’m gonna see ya
    I’m gonna meetcha meetcha meetcha meetcha
    One day, maybe next week
    I’m gonna meetcha, I’m gonna meetcha, I’ll meetcha
    
    I will, drive past your house
    And if, the lights are all out
    I’ll see who’s around
    Let's Go! 
Repeat