Being a former banker, banks do post no firearm signs and ask that customers do not carry guns into the bank. These signs are usually posted on the doors leading into the lobby. The reasoning is, anyone bringing a firearm into the bank is a potential bank robber. The last bank that I worked at had such signs that also told customers to remove sunglasses and sweatshirt hoods when entering the lobby. The pretense is to help the bank's staff identify its customers. The real reason is to help the bank's staff identify suspicious people. Each bank decides what its firearm policy is. Most do not allow carry of any sort. Perhaps you missed the posted sign, or if not, the bank needs to post the appropriate signage.