[this is a zombie (or maybe a ch’ombie 
) thread; but , hey , answers to grammar and language questions don’t change much in 12 years.]
The simple answer is :
Classical Hebrew has no “ch” sound (as in church). There are no proper ,authentic Hebrew words containing the “Ch”, and there is no letter in the classical Hebrew alphabet to express this sound.
But Modern Hebrew does have the ch sound: not in Hebrew words, but in slang words, and words that have been adopted from other languages.
And also, as mentioned above, in the the semi-slang pronunciation of the word for the number 19. (In proper Hebrew,the number 19 is “teesha-esray”.In common speech, this gets shortened to “T’sh-esray”, with the “t-sh” pronounced like the ch in church.
The modern Hebrew alphabet created a letter to write this sound–by adding an apostrophe to the letter Tzadi.
Also the ch sound is used in lots of slang/adopted words.
For example, the phrase “Chick-chock”, and the diminutive ending “chick”,which can be appended lots of words.