Yes direct debit through maxis accepts Amex. Just called maxis hotline earlier.

dont think that's possible, merchant usually begin to auto-debit on bill date itself, and since bill date varies on the day of the week, chances of maximizing the cash rebate is low.

Thanks for the explanation, cybpsych. To maximize cashback on M2C Amex, we have to manually pay for telephone and electricity bills.

Choosing the auto debit for telephone and electricity bills is definitely a no for us. 
I heard from Maxis Billing Department that they are choked with the enormous demand from customers, to charge the bill payments to their Amex card on 10 am on Saturday.