Change Name on PNG Document

I have a single document saved as a PNG image and I need the displayed name replaced with a completely different one. It is not just a spelling correction—I will supply you with the new name to insert... (Budget: £10 - £15 GBP, Jobs: Adobe Photoshop, GIMP, Graphic Design, Image Processing, Photo Editing, Photoshop, Photoshop Design, Visual Design)