"Cancel Subscription" clarification

[Sakuraluna]

I feel that If cancel my internet subscription, they'd disconnect my internet immediately.

Or is it common knowledge worldwide that I'd still be able to use my internet until the end of the month?
Does it vary with different company policies?
I'm confused

If you're paying per month and cancel halfway through a month it typically isn't going to end your service until the start of the next billing cycle, when you won't be charged again. That last part of the month that you're still active would have already been paid for at the last billing period unless you waited until right before you'd get charged to cancel. It does depend on the company, situation and the service in question, but from my experience this has always been the way SE has done it, as far as xiv is concerned anyway.