I'm hoping this means either "Is it OK if I pay my electricity bill by direct debit?" or "How do I (arrange to) pay my electricity bill by direct debit?", but which one is it?
Ah. The context is awkward to explain because it's a textbook exercise in which the wording changes when inserted into a contextual sentence. If it's ambiguous as a standalone sentence then I think I will thank you for your reply and move on.
銀行員：この口座、しばらくお使いになってないようで すね。このままだと毎月の維持費が発生してしまいます が。
客：電気代を自動引き落としにしたらどうですか。(How about arranging to pay my electricity bill by automatic debit from this account?)
銀行員：はい、それなら大丈夫です。
Yeah, I know this is a bit "unreasonable" example. 自動引き落としにするのはどうですか/したらどうなりますか is far more natural for the case. I think this one would be more possible, though.
@ the OP, ～たらどうですか is generally used to make a suggestion to the adressee.