[Invisible Mode] Block Group Invites
If someone is repeatedly inviting you with the intent to troll or harass, then it’s not a legitimate form of invitation. In that case you can report the person for harassment. Reports can either be done with the ingame system, which is what support prefers when possible, or by making a ticket (top of page-Support then top of page-Submit a Request).
If it’s showing up in chat so that it’s obvious what you are reporting, then use ingame. If it’s not obvious and you need to explain, make a ticket.