"We need to verify your subscription" for HBO Max

I get the message, "We need to verify your subscription.” And “Here are some things to try:  Follow these detailed steps to confirm if your plan is eligible and take action to get HBO Max™. Explore the HBO Max™ sign-in FAQ"

I get this message when I try to watch HBO Max on my iPhone or on my TV.  HBO Max is definitely included in my plan (I have Unlimited Choice(R) II plan).  I have been trying to access HBO Max for many months and spent hours trying to trouble shoot this on my own. Is there a customer service support line or email or chat option for resolving this? It seems deceptive to charge for this service and not actually make it available.