What's the penalty for stealing a person's $300 iphone at a bank?

My friend
Was caught on camera stealing a $300 iphone at his bank.
He sold the iphone for personal profit
Bank gave personal information to cops
He bought a new iphone for a cover up
He went to police station to give the phone back
Lady notice different iphone and wants original phone back…
My friend can't get the old iphone back. And is to return to the police station with orginal iphone.

What should he do and what will happen to him

Added (1). Note: He does not worth at the bank, nor does the victim of her stolen good.

Added (2). The iphone was left on the table alone as if he found it, but stoled it around people.
He did not use any intimidation or violence to steal the phone.

He will be way better off telling the truth. Your friend did the right thing by replacing what he stole. There's nothing he can do to get the original phone back and he has done the next right thing - replace it. By doing the right thing he has shown he knows he messed up but is willing to make it right.

If this is the first time he has been in this kind of trouble, he will probably get a very light punishment if any at all. Depending on his age it may not go on his record.

Your friend did a brave and honest thing by replacing the phone.

Did your friend use violence of intimidation to help him get the phone? Please provide details. Unclear if it is theft or robbery.

EDIT: OK. It looks like your friend will probably be charged with theft. Your friend is obviously not very smart. He stole a phone inside a bank which has a million security cameras and all of your personal information. Any jury would convict him in a heartbeat.

It sounds like a crime of opportunity (i.e. Your friend just saw the phone there and was tempted). Your friend should try to work out a plea bargain with the DA where he apologizes to the victims and compensates them for their losses. If your friend is a first time offender then the DA will probably be lenient since there was no violence, intimidation, or premeditation. I'm sure your friend has a lawyer who can figure all of this out. I wouldn't worry too much about it.