Still got a new bill after cancellation

I cancelled my internet service on 3/13/2026, and have returned the equipment to the store. However, I am still got a bill of $85.87 for a new month. My last paid service period was 2/23-3/22, so instead of a new bill of $85.87, I should see a refund of the extra 10 days after the cancellation. That said, in the "Upcoming Charges" page, I see a negative amount of -$114.07, which probably includes the refund and the new bill, but it's very confusing. The online assistant was not helpful. What can I do to fix it?