Are you 100% sure it was a form from a bank?
Everything stinks of a scammers phishing form, leading to scammer calls.
I expect the only time a bank is going to want your phone number is when you initially sign up with them. After that, they should know who you are and your contact details.
I almost got caught out by a “sorry we missed you” delivery message, until it was asking for my date of birth.
Some of these random emails and SMS can catch you off-guard and seem legit