Incorrect bill

My old xfinity contract was expiring, and I worked with an online agent to get a new contract to start the day after my old one expired. I received a confirmation email that my new bill would be X amount per month. However when I log into my xfinity account online, the new bill is about $15 more than what was confirmed. I have spoken to at least two online agents about this, and they both claim that a $15 credit has been applied to my account but they gave different timelines on when I would be able to see that reflected on my online account (one said it would be updated in 24 hours and the other said 2-3 hours, it sounded like they were just saying random numbers)--it's been days and I don't see any changes to my bill. What now?