Comparing

The meaning differs slightly by the financial institution. 「振替」refers to the transfer between the bank accounts of the same person. 「振り込み」 means to remit money to others. 「替」 here means "replacement." In essence, the person's property has not increased, but the amount of money in different accounts has been replaced. So "「振替」" is not difficult to understand.

The better one is お返しします. https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1176362646

 "以後" can be used as an adverb or placed after other words. 卒業以後、結婚しましょう！ 電話は８時以後にしてください。 以後、気をつけなさい。 "以降" cannot be used alone as an adverb. So it cannot be placed at the beginning of a sentence .  It can only be used as a suffix for words. 今月以降は、この住所に変わります。 １７時以降は個人の時間です。