When do I cancel my plan?

I spoke with customer service agent “Kyle” today (9/7/26) at 4:04pm and the call lasted around 10 minutes. I called to request that the last day of my service be October 22, 2026 because I am moving and the location I am moving to already has wifi so I can’t transfer my plan no matter what. He said it wouldn’t let him schedule that far out and that he couldn’t do anything for me. He said I need to call back closer to my move out date to cancel. When in October am I supposed to call? My service period is from 28th of the month prior until the current month on the 27th. My bill is due the 18th of each month, so would that make my last bill due November 18?