Monday Hour One

I blocked out time on my calendar to reach out to companies about returns and refunds. It is either phoning call centers or live chats. I batched them up. Now it is at the end of my allocated time but I am still on live chat with 2 companies. I don’t want to disconnect the call mid conversation as it would mean going through it all again. How can I handle situations like these where I can’t anticipate how long it will take to wait for a response?