We deployed functionality to our network that allows you to disable leave events so you are not billed for those transactions unless you are actually using the Presence add-on. If you do not have Presence enabled, and you want to prevent the 402 responses, you must suppress leave events when you init the PubNub instance.

JavaScript SDK v4

var pubnub = new PubNub({
    subscribeKey: "mySubscribeKey",
    publishKey: "myPublishKey",
    ssl: true,
    suppressLeaveEvents: true // <--- add this

JavaScript SDK v3

pubnub = PUBNUB({                          
    publish_key   : 'demo',
    subscribe_key : 'demo',
    ssl: true,
    NOLEAVE: true // <--- add this

The 402s should not affect your app negatively but if they do please report your incident to PubNub Support with the details.