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
I also got a million spam calls after applying for a mortgage with a trusted bank a couple years ago. I suspect that the banks sell your information to mortgage brokers. I'd be curious to see the privacy policy on the form you submitted.
I took out a loan, but the service request was in my partner's name. It's my phone, but now I'm getting crazy crypto spam WhatsApp stuff in her name, along with home security spam and other spam I never got before. Since it's coming to my phone, in their name, either or both companies sold me / us out and we were getting calls within days.
We had a zoom call with a very well reviewed, recommended broker local to us.
Next day I get a spam call pretending to be the bank we talked about the most as a lender, but that we currently have no business with.
My paranoia has been at 100% ever since
I had an employer that uses Santander for pension, within a day of them adding my info into Santanders systems my email that has never gotten spam before in over 10 years (custom domain, only every used for government stuff or employment stuff) got 20-30 spam emails.
It keeps getting 10 or so a day since then.