It sounds like the divorce and couples therapy is VERY hard for you. I think it would be very hard for me too. I have not ever canceled but I am not even close to married to someone. I think that I would have a miserable time if I was divorcing someone.
I suspect that your T would say "yes" and try to schedule an individual session if you requested one. He might even bring up your phone message in your couples session and schedule one for you. I doubt that your T is saying "no" or rejecting you. He probably just didn't get the message and will probably bring it up during the couples session. When is your next individual session with T? I hope you can get the guts to go to the session and tell T how you are feeling. He might need to slow down on some of the work that you are doing in couples therapy. Sometimes, our anxiety is a sign that our Ts are going to fast for us and need to slow down but Ts can't read our minds about this. So we need to let them know when they are running ahead of us.