Not being paid for my full time?

I am a presenter on tiktok with brands. This one brand I have been working with pays me by the hour... But when ive put in my invoice as I did 2 live shows for them and the hours I was asked to be there for were 1:30-6:30, They have said I can't charge 4 hours, I can only charge 3 hours as the actual live part was 3 hours long... But they have asked me to be there for 4 hours. So who's right? because as far as i'm concerned, If im there for 4 hours, getting ready before the live and de-breafing after the live, I have still worked for 4 full hours...

I have told them I expect the invoice to be paid in full and that if they do not want to agree to pay me for all my hours in the future, I will no longer work with the brand but those 2 hours they're trying to deduct from me is a lot of money...