In the US a while ago Citibank had a promotion that required signing up for a new account and depositing $15,000. So I did. My account was then frozen for "susp

In the US a while ago Citibank had a promotion that required signing up for a new account and depositing $15,000. So I did. My account was then frozen for "suspicious activity" due to a "large transfer into a new account" until I called them. Luckily a phone call was enough for them to unfreeze my account. I just found it so odd to consider doing a promotional requirement as suspicious... and I didn't know how long they could just keep my funds frozen like that. Seemed sketchy. What if I had checks that needed to clear?