AARP Plan G

I have AARP UHC Plan G. I want to set up my own payments monthly through my bank — not through UHC direct bank withdrawal. But I've called the member number and have received conflicting answers. One said that I cannot set up auto payments with my bank mailing the payments for me. Even though my bank would put my UHC Plan G membership number on each check, UHC will not accept the payment mailed from the bank without the monthly coupon. Is this accurate?

I have all my other monthly bills, credit cards, etc., set up through my bank, not through all the different companies. This makes it easier to see everything in one place.