Banking Institution Mislead Customers About Interest Rates

[GreatGeak]

If I got proof that a banking institution was misinforming their clients to believe that their savings account was wielding %5 interest monthly (when in reality it's yearly), could I make decent money in a lawsuit?
I was misinformed by 3 different tellers and 2 different institutions that it was monthly. until finally I received the interest and asked again, and was yet again informed that it was monthly, until the teller checked further, to find out that it was actually yearly.

EDIT:
Here is a formal complaint I sent the institution,
Hello,

I am emailing to write out a formal complaint based on an issue that I have with the way [Bank X] does business.
I was told by three different tellers at two different [Bank X] establishments that the Delta Savings account receives a 5% interest rate monthly. At one point I called and asked specifically if I would receive $75 off of the $1500 max that I invest in the delta savings account, the phone operator assured me that that's what I would make monthly.
I proceeded to transfer all my funds from my prior bank to [Bank X], I also proceeded to blab to all my friends how amazing [Bank X] was.
At the end of this last month, I checked my interest rate, to see that hard earned %5, only to discover it was not the entire %5...but how could that be so, I had the required 4 transactions on my credit account, and 7 transactions on my debit account. I called the third teller and asked yet again, yet again I was confirmed that it payed out monthly...when I explained that there must be an error as I don't have %5 in my account, she proceeded to double check with someone else and left me on hold for about 10 minutes. After she finally got back on, she proceeded to apologize and confirm the actual amount, and that is %5 yearly.

This is extremely poor business as I invested all my money in [Bank X] under the guise that I would be making %5 on my delta savings account.
Unfortunately as much as I like [Bank X]'s help and surroundings, I am extremely displeased with this unprofessional way of stealing over customers.

Sincerely,
[me]

P.S. To make clear, I also have two different friends (one who referred me) who were lead to believe the same thing.

[Mr. Knowitall]

I expect that you received extensive written information about the account, and that none of it suggests that the interest rate was anywhere close to 5% per month. Bernie Madoff built a $50 billion dollar Ponzi scheme offering annual returns of "only" 12-15% - you can't get 5% per month anywhere, save perhaps if you're a Mafia loan shark.

Frankly, the idea that a bank would give 5% monthly interest is so over-the-top ridiculous that I think you would have a difficult time convincing anybody of your story. Unless you're depositing six figures (and realistically even then) you should be overjoyed that you found a bank that is committing to 5% per year. Share the name of that bank that guarantees 5% annual return on a passbook savings account, and they'll be so overwhelmed with new business they'll be bursting at the seams with cash. Seriously - check out the competition.