Your part-time job pays for your shift, not your whole evening.

A job buys a set number of hours, and the trade stays fair as long as it stops at the edge of them. What leaks past the edge is everything else: the group chat after close, the guilt about an unanswered text, the replaying of something a customer said. None of that is on the schedule and none of it gets paid.

When your shift ends, mark the ending somehow. Change your shirt, take the long way, put your phone on silent for the walk home. If messages keep arriving on your own time, it is reasonable to say you read them when you are on the clock.