IPA: //ˈpoʊstpeɪd//
KK: /ˈpoʊstˌpeɪd/
Referring to a service or payment plan where the charges are paid after the service is used, rather than in advance.
Many mobile phone plans offer postpaid options that allow users to pay for their usage at the end of the billing cycle.
Postpaid → It is formed from "post-" (meaning after) and "paid" (from Old English "paidan", meaning to pay). The word "postpaid" refers to a payment that is made after the service has been rendered.
Think of making a payment 'after' ('post-') receiving a service — that's what postpaid means.
No commonly confused words.