One of the classic Messenger tropes. The quick solution is to temporarily block them for a bit.
millions have told him to stop. ur right also
what is it?
You mean, what is the trope? I don’t recall the preferred name, but idea is that you can block/unblock a user repeatedly in order to fill their screen up with toasts in the hope of getting their attention, as Dylan demonstrates above. Alternatively, if you wish to gain the attention of your entire contact list, you would quickly switch between Appear Offline and Online.
Among the more annoying aspects, this would be used to passively attempt to get someone to talk to you, without actually having to talk to them first, such as a person you were interested in at school.