Plan/billing change hasn't gone into effect

I changed my internet only plan to a lower tier (speed) via online live chat Thursday, 3/6/2025.  I received the confirmation email that same day, received new modem the day after and got it all set up.  However, when I do a connection check, it's showing the previous higher speed; when I check My Plan, it's showing the higher speed/more expensive previous plan, and when I check "upcoming charges," it's showing the same higher cost charges as before changes made.  I was of the impression plan/speed changes would go into effect immediately.  I'd love NOT to have to have another very long live chat, phone conversations even worse, but is there any other way that I can get this plan change/bill change straightened out?  Please and thank you!