Q: iphone 6 plus No Volume

Hello, I have a sound issue and don't know what happened. Please help! My iPhone 6 Plus has no volume, It stays in headphone mode with I try to turn up volume with external controls. I have sound at all unless I have headphones connected. I have to use speaker to make phone calls. No sound with Music or Video apps either. Any suggestions on what has happened. Thanks in advance for any suggestions!