Verizon adding $.66

I always pay my bill early (generally 5 days) when I get the email from Verizon that my bill is ready. The past 2 months they had added an extra $.25-$.66 to my account after it has been paid.

Does anyone have any idea why this is happening? Support said “if any extra charges are added, they are added to the next bill.” And here we are again in the same situation as last month.