This is the 10342nd most frequent Japanese word.
騙さ
"騙さ" is the stem form of the verb "騙す" (damasu), meaning "to deceive" or "to trick."
In this sentence, the word '騙さなかった' is used in its negative past form, indicating that no act of deception occurred by 'he' towards 'me'.
彼は私を騙さなかった。
He did not deceive me.
Here, '騙さないでください' is a polite request form, used to ask someone, in this context the swindler, not to perform the act of deception.
その詐欺師は多くの人を騙さないでください。
Please do not deceive many people, swindler.
The phrase '騙されない' uses a passive negative form, expressing the need for vigilance to avoid being deceived by others.