You've posted to a public forum, which implies you wanted help and/or clarification. Additionally other customers with similar issues may reference this thread, so it's important to clarify how the billing cycles work. This point of clarification is quite literally the root cause of your misunderstanding.
In any case, your best course of action is to contact @CS_Agent , which it sounds like you've done. If you setup autopay, they've taken the payment as agreed. It's possible because if it just happened that they may throw you a bone and reverse it out and put you on the new plan, but know that that would be an exception, not an expectation. If you never setup auto pay, then definitely share that information with the PM staff.
Also what most on here will typically recommend is to make the plan change whenever you want mid-cycle (so you don't have to time it for the last day), but ensure you select the option to take effect at your next renewal, rather that immediately. Then you don't have to time it out.
