1.How could someone get a hold of your credit card number?

get a hold of：取得

2. I know. It's just such reckless spending.

reckless spending：花钱如流水

3.I think when someone steals your credit card, they've kind of already thrown caution to the wind.

throw caution to the wind：把理智抛至脑后;鲁莽行事;恣意妄为

4.Oh, Monica. You are not still going over that thing.

go over ：仔细检查;认真讨论;用心思考

5. Well, it does not ring a bell with me...

ring a bell with：听起来耳熟