Late fees even though not late paying

[canada1439]

I get my income once a month, on the last business day of the month. And my Cogeco bills are due on the last business day also. If I pay them the moment I get the direct deposit, then I've made the payment ON the due date, but an operator from Cogeco told me that they "need" 3-4 days to "process" the payment, and that if I'm a few days late, they'll charge me a late fee. I make the payments online from my bank account, NOT by cheque, so there's no reason it should take 3-4 days for them to receive my money.

When we pay our bills online from our bank account these days, the transaction is instant, but companies still get away with claiming that they need 3-4 business days to "process" the transaction. I understand why credit card companies do it...if you owed them $1000, and fully paid it off on a certain date, they could sneakily continue collecting interest for an extra 3-4 days, even though you don't actually owe them money anymore. They can get away with it because the laws are based on the way things used to be, many years ago, when transactions were not done instantly with computers. But now that they are instant, is it still legal for companies to lie for 3-4 days and say that they haven't yet received your payment? Or has the law been updated, but not enforced? Is there anything I can do to prevent them from charging me a late fee when I'm not actually late?