How long does it take to cancel a contract??????

On the 27th of July 2021 I called and after a long wait, got through to retentions. I spoke to a helpful lady there and canceled my contract and deactivated the number. Here were are just more than a month later and I’m still getting charged a bill???? Last week I was on hold with retentions for just over an hour, and even now as I’m writing this I’ve been on hold for 20 min already. When customer care checked the reference number I gave them, they said that the number/contract has been canceled. So why am I still being charged????