Employer
Employee
noun
An employment (雇用) someone is someone who gives you employment, aka an employer.
こようしゃ
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
雇用者に新しい電話番号を何度も教えてるのに、いっつも古い方の番号に掛けてくるんだよな。
I’ve told my new phone number to my employer over and over again, but he always calls me at the old number.