There are brokers who will undertake to close your position with them at a pre-agreed level (i.e. a "guaranteed stop-loss") regardless of whether or not the market traded at that price, the speed of the market, intervening events, and whether or not they were able to close any position of their own at that price. In other words, they agree to settle your account as if the position closed at the specified price, regardless of subsequent events.
They usually charge for this in the form of extra spread, when the position's opened.
It's relatively expensive.
It's a significant additional profit-source for the brokerages who offer it.
I've never used them, myself: it wouldn't be worth it, for the type of trading I do.
What they choose to do is their business. If you've paid the premium for a guaranteed stop, they close your position with them at the specified level.
You need to read the fine print carefully, and discuss it with them.
For me, not using guaranteed stops works best, because the cost of using them would be disproportionately expensive for me (and I'm wording it mildly).